THE  CHEMISTRY  OF 

THE-NON-BENZENOID 
HYDROCARBONS- 

And  Their  Simple  Derivatives 


BY 

«-tx 

BENJAMIN  T.  BROOKS,  PH.D. 


First  Edition 


BOOK    DEPARTMENT 
The  CHEMICAL  CATALOG  COMPANY,  Inc. 

ONE  MADISON  AVENUE,  NEW  YORK,  U.  S.  A, 
1922 


COPYRIGHT,  1922,  BY 

The  CHEMICAL  CATALOG  COMPANY,  Inc. 
All  Rights  Reserved 


Press  of 

J.  J.  Little  &  Ives  Company 
New  York,  U.  8.  A. 


PREFACE 

The  beautiful,  interesting,  and  often  facile  chemistry  of  the  benzene 
hydrocarbons  has  somewhat  overshadowed  the  chemistry  of  the  ali- 
phatic open  chain  and  cyclic  non-benzenoid  hydrocarbons.  Certainly 
the  chemistry  of  the  former  series  has  been  much  more  fully  rounded 
out.  Judging  from  the  customary  method  of  treatment  accorded  them 
in  our  textbooks,  there  is  some  confusion  in  the  arrangement  of  subject 
matter  which  does  not  give  the  student  a  proper  idea  of  the  close  re- 
lationships and  similarity  of  chemical  behavior  possessed  by  all  the 
non-benzenoid  hydrocarbons.  Mr.  Wells,  in  his  "Outline  of  History," 
says:  "There  is  a  natural  tendency  in  the  human  mind  to  exaggerate 
the  differences  and  resemblances  upon  which  classification  is  based,  to 
suppose  that  things  called  by  different  names  are  altogether  different, 
and  that  things  called  by  the  same  name  are  practically  identical. 
This  tendency  to  exaggerate  classification  produces  a  thousand 
evils,  .  . ."  This  tendency,  which  Mr.  Wells  deplores,  is  well  shown  by 
the  use  of  the  term  "hydro-aromatic"  hydrocarbons  and  the  classifi- 
cation of  cyclohexane  and  its  derivatives  with  benzene.  This  term  is 
still  employed  for  cyclohexane  and  its  simple  derivatives,  although 
its  behavior  is  almost  identical  with  that  of  normal  hexane.  The  same 
applies  to  cyclopentane  and  its  simple  derivatives  as  compared  with 
normal  pentane,  yet  cyclopentane  cannot  be  termed  a  "hydro-aromatic" 
hydrocarbon.  Cycloheptane,  cyclooctane,  cyclononane,  cyclobutane 
and  cyclopropane  should  certainly  be  classed  and  described  together 
with  cyclohexane,  as  indeed  Aschan  and  a  few  others  have  done.  The 
differences  in  chemical  properties  between  benzenoid  ring  systems  and 
NON-BENZENOID  hydrocarbons  are  well  established,  but  in  spite 
of  the  enormous  amount  of  work  done,  have  not  yet  received  adequate 
explanation. 

As  regards  the  aliphatic  hydrocarbons  proper,  these  fare  very  badly 
in  most  works  on  organic  chemistry,  particularly  in  the  briefer  text- 
books. Usually,  the  entirely  erroneous  statement,  or  implication,  is 
made  that  the  so-called  type  reactions  given  for  the  first  two  or  three 
members  of  the  methane  series  hold  good  for  the  higher  members.  Be- 
yond the  fact  that  all  of  them  may  be  completely  burned  to  carbon 

3 

£.72442 

fc     *-W     1    ^£  rW 


4  PREFACE 

dioxide  and  water,  such  statements  are  hardly  in  accord  with  the 
known  facts.  We  note  that  the  chemistry  of  the  first  five  members  of 
the  methane  series  and  also  the  ten  carbon  atom  or  terpene  group, 
mostly  cyclic  hydrocarbons,  have  been  much  more  extensively  and 
carefully  studied  than  the  remainder.  Some  of  the  reasons  for  this 
are  fairly  apparent.  Thus,  the  essential  oils  afford  a  convenient  source 
of  substances  of  the  terpene  group  which  may  generally  be  isolated 
easily  in  a  state  of  purity.  The  natural  fatty  glycerides  or  other  con- 
venient sources  readily  yield  a  limited  number  of  fatty  acids,  nearly 
all  of  them  normal,  i.  e.,  acids  of  one,  two,  three,  four,  five,  six,  eight, 
ten,  twelve,  fourteen,  sixteen,  eighteen,  and  twenty-four  carbon  atoms. 
Research  in  many  of  these  special  fields  has  accordingly  been  greatly 
facilitated  by  the  availability  of  suitable  material  and  has  often  been 
much  stimulated  by  an  intimate  relation  to  industry. 

It  may  also  be  pointed  out  that  while  in  the  aromatic  series  a  rich 
variety  of  raw  materials  may  easily  be  isolated  or  prepared,  crystal- 
line derivatives  are  almost  the  rule,  permitting  easy  purification,  iden- 
tification, and  manipulation  in  small  quantities;  that  substitution  re- 
actions are  usually  capable  of  control  to  form  chiefly  one  product  or 
a  very  limited  number  of  products  or  isomers;  but  in  the  aliphatic 
series  this  is  not  the  case.  Petroleums  probably  contain  all  of  the  nor- 
mal paraffine  hydrocarbons  up  to  C26H54  and  perhaps  farther  in  the 
series,  and  perhaps  hundreds  of  naphthenes  which  are  for  the  most 
part  yet  unknown.  Not  only  is  it  at  present  impossible  to  isolate  pure 
individual  substances  from  this  complex  raw  material,  but  few  methods 
of  synthesis  applicable  to  the  higher  members  of  the  aliphatic  series 
or  the  more  complex  naphthenes  have  been  developed. 

The  reader  seeking  only  material  of  industrial  interest  may  object 
to  the  inclusion  of  much  subject  matter  which  is  solely  of  theoretical 
interest  and  the  searcher  who  scorns  industrial  processes  will  find  much 
in  the  present  volume  that  is  unorthodox.  The  author  desires  to  make 
no  apology  for  the  inclusion  of  both  classes  of  subject  matter;  the  de- 
scription of  any  special  subject  of  science  should  be  systematic  if  we 
are  to  retain  our  conception  of  science  as  classified  knowledge,  and  the 
author  does  not  feel  that  descriptions  of  industrial  processes  and  refer- 
ences to  patent  literature  detract  from  the  value  of  the  compilation, 
considered  as  a  scientific  monograph.  In  a  treatise  of  purely  industrial 
purpose  the  checker-board  plan,  in  which  economic  value  determines 
exclusion  or  inclusion  of  subject  matter,  may  perhaps  be  justified,  but 
the  author  believes  that  the  best  results  will  be  obtained  by  broader 


PREFACE  5 

scientific  treatment  of  industrial  subjects.  The  author  is  well  aware 
that  patent  literature,  in  spite  of  oaths  and  notaries'  seals,  is  not  bound 
by  the  same  standards  of  truth  that  govern  the  publication  of  purely 
scientific  papers  and  has  accordingly  treated  such  matter  critically  and 
with  caution. 

The  mechanical  art  and  engineering  of  petroleum  refining  has  been 
perfected  to  a  degree  which,  measured  by  profit  and  general  utility, 
deserves  commendation,  but  it  is  a  development  which  has  been  very 
little  dependent  upon  chemical  knowledge.  More  thorough  knowledge 
of  the  chemistry  of  the  non-benzenoid  hydrocarbons  will  surely  re- 
sult in  better  and  less  wasteful  methods  of  refining  and  may  lead  to  the 
conversion  of  petroleum  hydrocarbons  into  other  useful  products  by 
chemical  methods.  In  the  present  state  of  our  knowledge,  it  would  be 
rash  to  prophesy  what  may  be  accomplished  in  this  direction;  but  be- 
fore much  work  of  this  kind  can  be  done,  a  great  deal  of  painstaking, 
systematic  research  in  the  field  of  the  non-benzenoid  hydrocarbons  must 
be  carried  out  which  may  never  be  utilized  directly  in  an  industrial 
process.  The  writer  does  not  urge  research  in  this  field  solely  on  the 
ground  of  the  utility  of  the  possible  results.  Those  who  attempt  to 
justify  scientific  research  by  financial  returns  do  not  always  have  a 
very  strong  case,  and  to  attempt  to  balance  any  particular  industry 
upon  the  point  of  an  original  scientific  discovery  is  to  leave  out  of  ac- 
count the  contributions  of  a  host  of  other  people,  which  the  scientist 
seldom  appreciates.  Such  arguments  convince  nobody  and  often  arouse 
the  resentment  of  engineers  and  business  men  and  others  who  know 
better.  The  upbuilding  of  a  great  mass  of  information  and  generaliza- 
tions, new  experimental  methods  and  new  substances,  in  the  field  of 
the  non-benzenoid  hydrocarbons,  will  enable  industry  to  select  certain 
bits  of  knowledge  suited  to  further  progress  and  our  everyday  welfare. 
Every  original  investigator  making  real  contributions  to  the  fabric  of 
knowledge  is  thus  a  contributor  to  the  common  weal.  This,  while 
not  the  sole  justification  of  research,  is  the  correct  form  of  the  argu- 
ment of  the  utility  of  scientific  investigation. 

This  point  of  view  has  a  very  direct  bearing  on  the  question  of  re- 
search in  the  field  of  the  non-benzenoid  hydrocarbons.  The  petroleum, 
rubber,  turpentine  and  essential  oil  industries  stand  in  need  of  further 
systematic  theoretical  research  in  this  field  of  chemistry.  Work  along 
broad  lines,  involving  the  work  of  a  great  many  investigators  for  a 
great  many  years,  is  required.  American  chemists  have  heretofore 
played  a  singularly  insignificant  part  in  this  field  of  research  and  to 


6  PREFACE 

realize  this  it  is  only  necessary  to  mention  the  names  of  Wallach,  Sir 
William  H.  Perkin,  Jr.,  Semmler,  Engler,  Grignard,  Sabatier  and  the 
Russian  group,  Ipatiev,  Kishner,  Markownikow,  Wagner,  Konowalow, 
Zelinsky,  Aschan,  Bredt,  Ostromuislenski,  Lebedev,  Gustavson,  Char- 
itschkov,  and  others.  All  of  these  men  have  exercised  their  influence 
in  universities  or  technical  schools,  and  the  inference  may  accordingly 
be  drawn  that  we  must  look  to  our  American  universities,  rather  than 
to  the  petroleum  or  other  industrial  interests,  to  initiate  and  carry  on 
such  research  in  America.  And  if  the  American  petroleum  industries 
second  their  efforts,  as  the  Nobel  Brothers  have  done  in  Russia,  a  vast 
amount  of  work  of  permanent  scientific  and  potential  industrial  value 
can  be  done. 

The  present  monograph  is  not  a  catalog  of  all  the  hydrocarbons 
which  might  be  described.  The  writer  has  endeavored  to  show  the 
close  relationships  which  hold  generally  throughout  the  chemistry  of 
the  non-benzenoid  hydrocarbons  and,  on  the  other  hand,  to  point  out 
that  the  chemical  behavior  of  the  more  complex  hydrocarbons  of  the 
paraffine  series  and  the  alicyclic  hydrocarbons  cannot  be  assumed  from 
the  chemical  behavior  of  a  few  of  the  simpler  hydrocarbons.  The  chem- 
istry of  the  ethylene  bond  is  emphasized  because  of  its  great  impor- 
tance and  because  most  of  our  knowledge  of  its  behavior  under  dif- 
ferent circumstances  and  influences  is  empirical. 

Much  important  work  has  been  done  since  the  appearance  about 
twenty  years  ago  of  Aschan's  "Alicyclische  Verbindungen"  and  Semm- 
ler's  admirable  volumes  on  the  terpenes  and  this  work  has  been  briefly 
reviewed  and  the  attempt  has  been  made  to  treat  it  in  such  a  way  that 
will  be  helpful  in  wider  fields  of  organic  research. 


TABLE  OF  CONTENTS. 

PAGE 

CHAPTER  I.    THE  PARAFFINES 13 

1.  Occurrence  of  the  paraffines  in  nature. — a.  Natural  gas; 
composition,  behavior  under  pressure;  separation  of  the  con- 
stituents.— b.  Petroleum:  difficulty  of  isolating  simpler 
members  of  the  paraffine  series:  paraffines  produced  by  bio- 
logical processes;  general  character  and  probable  mode  of 
origin  of  petroleums. — c.  Other  natural  sources  of  paraffines. 
—2.  Formation  of  the  paraffines. — a.  Pyrolysis  of  organic 
matter;  effects  of  heat  on  non-benzenoid  hydrocarbons;  oil 
gas ;  formation  of  aromatic  hydrocarbons ;  the  gasoline  prob- 
lem.— 6.  Synthesis  of  the  paraffines. — Alkyl  halides  and 
metallic  couples;  the  Grignard  reaction;  reduction  of  alco- 
hols or  alkyl  iodides  by  hydriodic  acid;  catalytic  hydro- 
genation  of  olefines;  miscellaneous  special  methods. 

CHAPTER    II.     CHEMICAL    PROPERTIES    OF    SATURATED    HYDRO- 
CARBONS        52 

1.  Oxidation;  conversion  of  paraffine  wax  to  fatty  acids  by 
air  oxidation;  hardening  of  petroleum  residuums  by  blowing 
with  air. — Other  oxidizing  reagents:  2.  Behavior  to  nitric 
acid;  nitration  with  dilute  nitric  acid. — 3.  Alkyl  halides. — 
General  methods  for  preparing  alkyl  chlorides,  bromides  and 
iodides;  dissociation  of  the  simpler  alkyl  halides  by  heat; 
behavior  of  alkyl  halides  to  alcoholic  alkali;  general  reac- 
tions. 

CHAPTER  III.  THE  PARAFFINE  HYDROCARBONS  ....  76 
1.  Methane;  oxidation;  inflammability;  chlorination ;  syn- 
thesis from  water  gas  or  carbon  monoxide. — 2.  Ethane, 
propane,  butanes. — 3.  The  pentanes;  hexanes;  heptanes. — 
4.  Octanes;  synthesis  of  octanes  as  typical  of  methods  now 
known;  nonanes  and  decanes. — 5.  Paraffines  C10H22  to 
C6oH122;  paraffine  wax  from  petroleum. — 6.  Table:  Physi- 
cal properties  of  the  paraffines. — 7.  Notes  on  the  refining  of 
petroleum  distillates. 

CHAPTER  IV.    THE  ETHYLENE  BOND Ill 

1.  Recent  conceptions  of  valence  and  the  ethylene  bond; 
Baeyer's  strain  theory;  stability  of  the  ethylene  bond  and 

7 


TABLE  OF  CONTENTS 

PAGE 

carbocyclic  structures. — 2.  Chemical  properties  of  unsatu- 
rated  substances  of  the  ethylene  type. — a.  Modification  of 
the  chemical  behavior  of  the  ethylene  bond  by  substituents ; 
influence  of  the  double  bond  on  the  chemical  behavior  of 
substituents. — b.  Addition  reactions,  halogens,  halogen 
acids,  hypochlorous  acid,  aqueous  mineral  acids  and  the 
addition  of  water. — c.  Unsaturated  hydrocarbons  and  sul- 
furic  acid;  refining  of  petroleum  oils. — d.  Auto-oxidation  — 
e.  Reaction  with  sulfur  and  sulfur  chloride;  vulcanization 
of  rubber. — /.  Ozonides:  Use  of  ozone  in  determining  con- 
stitution.— g.  Properties  of  the  HC  =  CH  —  CO  group. — 
h.  Addition  reactions  frequently  used  for  identification  of 
unsaturated  hydrocarbons;  nitrosyl  chloride,  nitrous  acid; 
use  of  nitrosyl  chloride  for  the  synthesis  of  ketones. — 
i.  Other  substances  which  combine  with  the  ethylene  bond, 
aniline,  urea,  hydrogen  sulfide,  hydrocyanic  acid,  etc.— 
3.  The  preparation  of  unsaturated  hydrocarbons:  Decom- 
position of  saturated  hydrocarbons,  alcohols  and  organic 
halides  by  heat;  barium  soaps  and  sodium  ethoxide;  the 
Grignard  reaction;  exhaustive  methylation  of  amines. 


CHAPTER  V.    THE  ACYCLIC  UNSATURATED  HYDROCARBONS  .         .158 

1.  Ethylene,  physical  properties,  chemical  behavior;  pro- 
duction from  acetylene,  from  ethyl  alcohol;  coal  gas,  oil 
gas;  catalytic  oxidation  to  formaldehyde;  |3p-dichloroethyl 
sulfide;  reaction  with  sulfuric  acid  and  the  industrial  syn- 
thesis of  alcohol;  Hofmann  and  Sand's  ethanol  compounds. 
—2.  Propylene;  physical  properties  and  general  chemical 
behavior  and  rules  of  addition;  industrial  propyl  alcohols. 
— 3.  Butylenes  and  amylenes;  chemical  behavior. — 4.  Ole- 
fines,  six  to  nine  carbon  atoms;  difficulty  of  synthesis  or 
separation  of  pure  hydrocarbons. — 5.  Decene's  and  ali- 
phatic terpenes;  myrcene,  ocimene  and  allo-ocimene. — 6. 
Derivatives  of  2 . 6-dimethyl-octane ;  the  citral  group;  gera- 
niol  and  citral  a  nerol  and  citral  6;  linalool;  citronellol; 
a-  and  (3-ionone;  irone. — 7.  Sesquicitronellene ;  spinacene. — 
8.  Cholesterylene  and  its  relation  to  cholesterol. 

CHAPTER  VI.    POLYMERIZATION  OF  HYDROCARBONS      .        .        .    210 

1.  Substituted  ethylenes  and  the  effect  of  substituents  on 
polymerization;  the  conjugated  dienes,  their  chemical  be- 
havior and  the  synthesis  of  rubbers. — 2.  The  constitution  of 
rubber,  its  depolymerization ;  review  of  research  on  the  syn- 
thesis of  rubber;  raw  materials '  and  the  question  of  indus- 
trial synthesis. — 3.  Methods  of  polymerization. 


TABLE  OF  CONTENTS  9 

PAQB 

CHAPTER  VII.    CYCLIC  NON-BENZENOID  HYDROCARBONS    .        .    233 

1.  General  methods  of  synthesis. — By  polymerization  of  un- 
saturated  hydrocarbons;  decomposition  of  calcium  and 
barium  salts  of  dicarboxylic  acids;  condensation  of  dicar- 
boxylic  acid  esters  by  sodium;  by  sodium  and  malonic  acid 
ester;  the  Grignard  reactions;  dihalogen  derivatives  and 
sodium;  disodium  derivatives  of  carboxylic  acids  and  iodine 
or  bromine;  ring  closing  by  elimination  of  water  from  alde- 
hydes; diazoacetic  ester  and  the  synthesis  of  cyclopropane 
derivatives;  condensation  of  nitriles  by  sodium  ethylate  to 
imino  compounds  and  their  hydrolysis;  Kishner's  hydrazine 
method;  hydrogenation  of  benzenoid  hydrocarbons. — 2. 
Cyclopropane  and  its  simple  derivatives. — 3.  Cyclobutane 
and  its  simple  derivatives.-— 4.  Cyclopentane  and  its  simple 
derivatives. — a.  Syntheses  from  cyclopentanone. — b.  Naph- 
thenic  acids,  synthetic  and  from  petroleums. — c.  Substi- 
tuted cyclopentanes. 

CHAPTER  VIII.    CYCLIC  NON-BENZENOID  HYDROCARBONS:   THE 

CYCLOHEXANE  SERIES 278 

1.  The  hydrogenation  of  benzene;  catalytic  production  of 
cyclohexanols  and  cy clohexanone ;  cyclohexene  and  cyclo- 
hexadienes. — 2.  Alkyl  derivatives  of  cyclohexane,  synthetic 
and  from  petroleum;  cantharene. — 3.  Mono-cyclic  sesqui- 
terpenes. 

CHAPTER   IX.    CYCLIC   NON-BENZENOID   HYDROCARBONS:    THE 

PARA-MENTHANE  SERIES 315 

1.  Limonene  and  dipentene;  carvomenthene ;  para-men- 
thane;  the  constitution  of  limonene;  syntheses  of  limonene 
and  the  terpineols. — 2.  Terpinolene  and  the  terpinenes; 
Semmler's  carvenene. — 3.  Crithmene. — 4.  The  oxides;  gen- 
eral behavior  of  oxides;  1.8-cineol,  1.4-cineol,  pinol  and 
ascaridol. — 5.  Other  menthenols. — 6.  Menthol;  stereochem- 
istry of  menthol  and  menthone;  the  menthenones,  piperi- 
tone  and  pulegone;  Buchu  camphor;  carvone. — 7.  The  phel- 
landrenes. 

CHAPTER  X.    CYCLIC  NON-BENZENOID  HYDROCARBONS:  ORTHO- 

AND  META-MENTHANE  DERIVATIVES 384 

1.  Sylvestrene;  Its  synthesis  from  carvone;  Perkin's  syn- 
thesis.— 2.  Ortho-menthane  derivatives;  synthesis  by  Per- 
kin. 


10  TABLE  OF  CONTENTS 

PAGE 

CHAPTER  XI.    CYCLIC  NON-BENZENOID  HYDROCARBONS:  BICYC- 

LIC  AND  TRICYCLIC  HYDROCARBONS 396 

1.  Santene. — 2.  Sabinene,  thujene  and  carene. — 3.  Tetra- 
hydro  and  decahydronaphthalene. — 4.  Hydrogenation  of 
indene,  anthracene  and  phenanthrene. — 5.  Nomenclature  of 
bicyclic  and  tricyclic  hydrocarbons. — 6.  Bicyclic  and  tri- 
cyclic  sesquiterpenes. 

CHAPTER  XII.    BICYCLIC  NON-BENZENOID  HYDROCARBONS:  THE 

PlNENES  AND  FENCHENES 420 

1.  Character  of  commercial  turpentines. — 2.  Constitution  of 
a-pinene;  chemical  reactions  of  a-pinene. — 3.  Beta-pinene; 
synthesis  and  constitution. — 4.  Bornyl  chloride  and  its  de- 
composition products. — 5.  Pinolene;  tricyclene;  the  fen- 
chenes. 

CHAPTER  XIII.  BICYCLIC  NON-BENZENOID  HYDROCARBONS:  CAM- 

PHENE,  BORNYLENE  AND  CAMPHOR      .  .  .  .  .      453 

1.  Review  of  research  of  the  constitution  of  camphene  and 
bornylene. — 2.  a.  Camphor;  constitution  of  camphor  and 
its  oxidation  products;  camphoric  and  related  acids. — 
b.  Epicamphor. — c.  Derivatives  of  camphor. — 3.  Synthetic 
camphor. — a.  Plantation  camphor  vs.  synthetic  camphor. — 
b.  The  preparation  of  bornyl  chloride;  conversion  of  bornyl 
chloride  to  camphene,  bornyl  acetate  and  borneol;  hydra- 
tion  of  camphene  to  borneol. — c.  Other  processes  for  the 
conversion  of  pinene  to  borneol;  the  Thurlow  and  similar 
processes. — d.  Oxidation  of  the  borneols;  impurities  in  syn- 
thetic borneols  and  camphor. 

CHAPTER  XIV.  CYCLIC  NON-BENZENOID  HYDROCARBONS  :  CYCLO- 
HEPTANE,  CYCLO-OCTANE,  CYCLONONANE  AND  POLYNAPH- 
THENES 511 

1.  Cy cloheptane ;  cycloheptene,  cycloheptadiene  and  cyclo- 
heptatriene. — 2.  Cycloheptanone ;  eucarvone. — 3.  Cyclo- 
octane;  cyclo-octotetrene. — 4.  Cyclononane. — 5.  Polynaph- 
thenes;  lubricating  oils. 

CHAPTER  XV.    REARRANGEMENTS .524 

Cyclobutane  and  cyclopentane  derivatives;  a-pinene  and 
bornyl  chloride;  cyclobutyl  amine  to  cy clopentanol ;  cyclo- 
pentane and  cyclohexane  derivatives;  Meerwein's  researches 
on  pinacones;  borneol  and  camphene. 


TABLE  OF  CONTENTS  11 

PAOB 

CHAPTER  XVI.    PHYSICAL  PROPERTIES 538 

1.  Density  and  molecular  volume;  melting-point  and  boil- 
ing-point.— 2.  Optical  properties;  absorption  of  light,  color 
and  fluorescence;  molecular  refraction  and  influence  of 
structure  on  refractivity ;  molecular  dispersion ;  magnetic 
rotation;  optical  activity  and  methods  of  synthesis  of  opti- 
cally active  hydrocarbons;  optical  activity  of  petroleum. — 
3.  Thermochemistry  of  the  non-benzenoid  hydrocarbons; 
specific  heat;  latent  heat  of  vaporization;  heat  of  combus- 
tion.— 4.  Dielectric  constants;  static  charges  of  oils  pro- 
duced by  friction;  transformer  oils. — 5.  Viscosity;  effect  of 
ring  closing  on  viscosity;  viscosity  of  petroleum  oils;  vis- 
cosity and  lubrication;  effect  of  dissolved  paraffine  on  vis- 
cosity of  oils. — 6.  Solubility;  petroleum  fractions  in  other 
solvents;  paraflme  wax  in  various  solvents;  terpene  hydro- 
carbons in  dilute  alcohol;  solubility  of  methane  and  other 
gases  in  oils;  sulfur  in  petroleum  oils;  dissolved  sulfur  in 
rubber;  liquid  sulfur  dioxide  as  a  solvent  for  unsaturated 
hydrocarbons  and  Edeleanu's  refining  process. — 7.  Colloids; 
greases  and  jellies;  emulsions;  adsorption  and  the  use  of 
fuller's  earth;  fractional  separation  of  hydrocarbons  by 
fuller's  earth. 

CHAPTER  XVII.    PHYSIOLOGICAL  AND  RELATED  PROPERTIES        .    591 

1.  Odor. — 2.  Physiological  effects;  narcotic  action  of  the 
simpler  hydrocarbons;  terpene  alcohols  and  ketones;  nat- 
ural and  synthetic  camphor;  halogen  derivatives  of  the 
paraffines. 


Chapter  I.     The  Paraffines 

In  any  systematic  treatment  of  the  non-benzenoid  hydrocarbons, 
it  is  difficult  to  subdivide  the  subject  matter  into  divisions  or  chapters, 
which  do  not  unduly  emphasize  minor  class  differences.  Thus  cyclo- 
hexane  is  not  ordinarily  considered  as  a  paraffine  or  saturated  hydro- 
carbon although  its  chemical  behavior  might  very  properly  place  it  in 
this  class.  On  the  other  hand,  the  cyclopropane  ring  frequently  ex- 
hibits properties  of  unsaturation  which  are  nearly  identical  with  those 
characteristic  of  the  ethylene  bond.  However,  since  a  discussion  of  the 
hydrocarbons  of  the  series  CnH2n+2  may  rationally  serve  as  a  ground 
work,  this  series  will  be  considered  first. 

Occurrence  of  the  Paraffines. 

From  the  economic  standpoint  by  far  the  most  important  natural 
sources  of  the  paraffine  hydrocarbons  are  natural  gas  1  and  petroleum. 
The  industrial  utilization  of  natural  gas  has  been  practically  limited 
to  the  United  States,  although  the  Chinese  may  claim  priority  as  re- 
gards its  first  industrial  use  since  old  Chinese  writings  describe  its 
collection  from  shallow  dug  wells,  piping  through  tubes  of  bamboo  and 
burning  for  the  evaporation  of  brine. 

Since  practically  all  the  natural  gas  produced  in  the  United  States 
is  consumed  as  fuel  or  burned  for  the  production  of  carbon  black,  very 
little  attention  has  been  paid  to  its  chemical  composition.  In  rare  in- 
stances natural  gas  contains  as  much  as  95  per  cent  methane  but  an 
average  gas  contains  about  85  per  cent  methane,  1.0  to  3  per  cent 
nitrogen  and  12  to  15  per  cent  ethane  and  other  paraffines.  Unusual 
geological  conditions,  but  little  understood,  result  in  gases  containing 
large  percentages  of  nitrogen,  hydrogen  sulfide  or  carbon  dioxide.  Hy- 
drogen sulfide  is  normally  not  a  constituent  of  natural  gas  but  is  fre- 
quently encountered  in  gases  in  the  Gulf  Coast  territory.  Nitrogen 
occurs  in  the  gas  of  the  northern  Texas  fields  to  the  extent  of  about  38 
per  cent  and  it  is  of  interest  to  note  that  this  gas  also  contains  helium 

1  In  1917  the  consumption  of  natural  gas  in  the  United  States  was  795  billion 
cubic  feet.  (Northrop  in  Westcotts'  "Handbook  of  Natural  Gas,"  p.  106.) 

13 


14     [CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

'hi  amtiunts  sufficient  for  its  extraction  on  a  large  scale  for  filling  dirig- 
ible balloons.  The  composition  of  natural  gas  is  usually  reported  in 
terms  of  methane  and  ethane,  these  percentages  being  derived  by  cal- 
culation from  the  results  of  combustion  in  an  explosion  pipette.  That 
hydrogen  does  not  occur  in  natural  gas  is  now  generally  accepted, 
Philipps  2  having  shown  that  the  early  analyses  in  which  hydrogen 
was  reported,  were  faulty.  Typical  analyses  reported  by  Burrell  and 
Oberf ell 3  are  as  follows : 

TYPICAL  ANALYSES  OF  NATURAL  GAS. 

B.T.U.per 

cu.  ft. 

CH4           C2H«       C02           N2  Oa  (760mm. 

Source  of  Gas                       %             %            %             %  %  O°C.) 

Texarkana,  Ark 96                0.0           0.8             3.2  0.0  1,022 

Noblesville,  Ind 86.8             6.2           0.8             6.2  0.0  1,040 

Leavenworth,  Kan 91.3             4.5           0.8             3.4  0.0  1,066 

Erie,  N.  Y 79.9           15.2           0.0             4.9  0.0  1,134 

Columbus,  0 80.4           18.1           0.0             1.5  0.0  1,193 

Guthrie,  Okla 69.4           20.6           0.1             9.9  0.0  1,062 

Muskogee,  Okla 92.1             4.1           0.4             3.4  0.0  1,057 

Pawhuska,  Okla 66.5           20.7           0.3           12.5  0.0  1,093 

Fort  Worth,  Tex.4 51.3           10.4           0.1           38.2  0.0  740 

Bow  Island,  Canada  *  ...    87.6  0.9  . .  11.2 

The  percentages  of  methane,  ethane,  propane  and  higher  methane 
homologues  can  be  determined  accurately  by  fractional  distillation  at 
low  temperatures.5  Thus  a  sample  of  natural  gas  supplied  to  the  city 
of  Pittsburgh  in  1915  was  shown  to  have  the  following  composition: 

Methane    84.7  per  cent. 

Ethane    9.4    "       " 

Propane    3.0    ' 

Butane  and  other  hydrocarbons 1.3    "       " 

Nitrogen    1.6    "       " 

In  recent  years  the  practice  of  removing  the  light  gasoline  vapors, 
mostly  butane,  pentane  and  hexane,  by  absorption  and  compression 
methods  has  become  almost  universal,  at  least  where  large  gas  supplies 
are  available.  High  pressure  gas  from  new  fields  contains  relatively 
very  little  gasoline  vapor,  the  highest  yields  being  obtained  from  low 
pressure  gas  associated  with  petroleum.6  The  removal  of  gasoline  va- 

*Am.  Chem.  J.  16,  406    (1894). 

aTJ.  S.  Bur.  Mines.  Techn.  Paper  109. 

4  This  gas  in  northern  Texas  contains  about  0.9%  helium  which  is  being  separated 
at  the  U.  S.  Government  plant  at  Petrolia,  Texas.  The  Canadian  gas  contains  0.33% 
helium. 

"Burrell,  Seibert  &  Robertson.     U.  S.  Bur.  Mines.  Techn.  Paper  10^  (1915). 

6  The  yield  of  gasoline  obtained  by  absorption  methods  from  so-called  dry  gas 
is  from  0.5  to  0.75  gallons  per  1000  cubic  feet.  When  the  initial  gas  pressure  is 
300  to  500  pounds  per  square  inch  the  yield  of  gasoline  by  the  absorption  method 
is  about  0.3  gallon  per  1000  cubic  feet.  The  compression  method  alone  is  not  employed 
when  the  gas  contains  less  than  0.75  gallons  of  gasoline  per  thousand  cubic  feet 
of  gas. 


THE  PARAFFINES  15 

pors  slightly  lowers  the  fuel  value  of  the  gas,  normally  one  gallon  of 
gasoline  per  1000  cubic  feet  lowering  the  calorific  value  of  the  gas 
about  5  per  cent.7  The  yield  of  carbon  black  is  considerably  dimin- 
ished by  the  removal  of  gasoline  vapors  from  the  gas.  In  common 
practice  the  average  yield  of  carbon  black  was  about  1  pound  per  750 
cubic  feet  when  very  rich,  low  pressure  gas  was  employed  for  this  pur- 
pose. The  behavior  of  natural  gas  under  pressure  is  of  industrial  im- 
portance from  another  standpoint,  i.  e.,  the  measuring  or  metering  of 
gas  under  pressure.  Although  the  gas  pressure  of  new  wells  in  new 
fields  may  be  as  high  as  1600  pounds  per  square  inch,  it  is  usually 
necessary  to  compress  the  gas  from  lower  pressures  to  about  650  pounds 
per  square  inch  for  transmission  through  long  pipe  lines.  Methane 
deviates  considerably  under  pressure,  from  the  behavior  of  a  perfect 
gas  and  Amagat 8  has  shown  that  at  40  atmospheres  it  is  about  9  per 
cent  more  compressible  and  at  100  atmospheres  is  17  per  cent  more 
compressible  than  a  perfect  gas.  Burrell  and  Robertson 9  have  shown 
that  the  average  natural  gas  is  considerably  more  compressible  than 
pure  methane,  at  35.5  atmospheres  this  deviation  amounting  to  about 
15  per  cent  as  compared  to  the  compressibility  of  a  perfect  gas. 

The  fuel  value  of  natural  gas  is  commonly  given  as  1000  B.T.U. 
per  cubic  foot  measured  at  0°C  but  owing  to  the  presence  of  ethane 
(1719  B.T.U.  per  cubic  foot)  and  other  hydrocarbons,  the  value  1100 
B.T.U.  is  a  better  average  value.  Since  in  ordinary  fuel  practice  the 
water  formed  in  the  combustion  is  practically  never  condensed,  the 
latent  heat  of  evaporation  of  this  water  should  be  deducted  to  give  a 
net  heating  value.10 

Ethane,  propane  and  butane  may  easily  be  separated  from  natural 
gas  in  conjunction  with  the  removal  of  gasoline  vapors  and,  as  Burrell 
and  Robertson  have  shown,  each  of  these  hydrocarbons  may  be 
isolated  in  a  very  pure  state  by  fractional  distillation  at  low  tempera- 
tures. In  view  of  the  low  cost  of  the  separation  of  oxygen  and  nitro- 
gen by  liquid  air  methods,  it  is  certain  that  pure  ethane,  propane  and 
butane  could  be  made  available  in  large  quantities  at  very  low  cost. 
These  hydrocarbons  are  not  now  utilized  (other  than  as  fuel),  but 
research  in  the  direction  of  their  chemical  utilization  is  in  progress. 

TDow.     TL  S.  Bur.  Mines.  Techn.  Paper  253   (1920). 

"Landolt  &  Bornstein.     Physikalische  Tabellen,  1905,  65. 

•U.   S.  Bur.  Mines,  Techn.   Paper  104    (1915). 

10  Richards,  "Metallurgical  Calculations,"  Ed.  1918,  p.  25,  gives  the  net  heating 
value  of  970  B.  T.  U.  for  methane,  the  water  formed  remaining  uncondensed.  Cf 
Waidner  &  Mueller,  "Industrial  Calorimetry,"  U.  S.  Bur.  Standards,  Techn.  Paper  S6 


16        CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

The  deviation  of  ethane,  propane  and  butane  from  the  behavior  of 
a  perfect  gas  is,  of  course,  greater  than  is  the  case  with  methane,  and 
when  compressing  gas  mixtures  containing  all  of  these  hydrocarbons, 
as  in  the  separation  of  gasoline  from  natural  gas  by  compression,  the 
behavior  is  the  resultant  of  many  factors  and  the  most  efficient  method 
of  operating  a  compression  plant  for  the  production  of  gasoline  can, 
at  the  present  time,  be  determined  only  by  experiment.11  According 
to  well  understood  principles,  when  the  pressure  on  a  gas,  containing 
condensable  vapors  is  increased,  the  partial  pressure  of  the  vapor  in- 
creases until  its  saturation  pressure  is  reached  at  which  point  conden- 
sation to  liquid  begins.  Thus  if  a  gas  is  saturated  with  pentane  vapor 
at  atmospheric  pressure,  compression  to  two  atmospheres  will  liquefy 
one-half  of  the  pentane;  if  the  partial  pressure  of  the  pentane  is  origi- 
nally one-tenth  the  saturation  pressure,  then  compression  to  ten  atmos- 
pheres will  be  required  to  reach  the  saturation  point  and  this  pressure 
must  then  be  doubled,  i.e.,  to  twenty  atmospheres,  to  liquefy  one- 
half  the  pentane.  But  when  other  condensable  hydrocarbons  are  pres- 
ent, these  simple  relations  no  longer  hold  true.  The  importance  of  re- 
moving the  heat  resulting  by  compression  is  indicated  by  the  accom- 
panying figures  showing  the  vapor  pressure  curves  of  the  simpler  nor- 
mal paraffine  hydrocarbons.  See  also  vapor  pressure  curves  of  the 
simpler  paraffines  on  page  88. 

Few  petroleums  consist  mainly  of  hydrocarbons  of  the  paraffine 
series,  but  the  lighter,  low  boiling  fractions  of  most  petroleums  consist 
of  these  hydrocarbons  almost  exclusively.  Particularly  is  this  true  of 
light  Pennsylvania  oil.  Since  much  of  the  earlier  chemical  work  on 
petroleum  was  carried  out  with  distillates  of  this  particular  oil,  it  is 
often  erroneously  stated  that  "American"  petroleum  consists  of  paraf- 
fines and  "Russian  petroleum"  consists  of  naphthenes  and  polynaph- 
thenes  of  the  series  CnH2n,CnH2n_2,  etc.  Generally  it  may  be  said  that 
the  petroleums  of  no  two  producing  regions  are  the  same.  Although 
the  petroleum  typical  of  the  Pennsylvania  field  probably  contains  the 
largest  per  cent  of  paraffines,  the  higher  boiling,  viscous  fractions  of 
this  crude  contain  but  a  few  per  cent  of  CnH2I1+2  hydrocarbons  and 
these  are  removed  by  chilling,  thus  manufacturing  the  "paraffine  wax" 
of  commerce.  Lubricating  oil  derived  from  Pennsylvania  and  other 
petroleums  consists  chiefly  of  hydrocarbons  of  the  class  CnH2n_2,12  but 
their  structure  is  unknown  and  no  pure  individual  hydrocarbons  have 

"Mabery,  Am.  Chem.  J.  1305,  231. 

"  Anderson,  J.  Ind.  d  Eng.  Chcm.  12,  547  (1920)  ;  Dykema,  U.  S.  Bur.  Mines. 
Bull.  151  (1918). 


THE  PARAFFINES 


17 


been  isolated  from  them.     Vaseline  isolated  from  Pennsylvania  pe- 
troleum, is   a  mixture  of  hydrocarbons   of  the   empirical   formulae 

Degrees  Fahrenheit. 
-13    +32      77      122     167     212     257    302     347     392    437     482     527     572 


Critical  34.3    50  At. 

Critical  102°  48.3  At. 


-50    -25 


50       75       100     125     150     175     200     225     250      275     300 
Degrees  Centigrade. 


Vapor  pressure  curves  of  the  simpler  paraffine  hydrocarbons.     (W.  O.  Snelling 
in  Hamor  and  Padgett's  "Examination  of  Petroleum.") 

CnH2n_2  and  CnH2n_4.  Petroleums  from  certain  American  fields  con- 
tain no  parafnnes,  for  examples,  Coates  13  has  shown  that  the  lighter 
distillates  of  the  oil  from  the  Jennings,  Louisiana,  field  consist  exclu- 
sively of  cyclic  hydrocarbons  of  the  CnH2n  series. 

18  J.  Am.   Chem.  8oc.  28,  384   (1906). 


18        CHEMISTRY  OF  THE  NON-BENZEN01D  HYDROCARBONS 

The  paraffine  wax  of  commerce  consists  of  a  mixture  of  hydro- 
carbons of  the  paraffine  series  from  about  C22H46  to  C.,6H54.  The 
natural  waxes  of  the  ceresin  type  are  evidently  not  normal  paraffines 
but  isomeric  hydrocarbons  probably  identical  with  the  amorphous  wax 
of  petroleum  oils  (see  below). 

The  number  of  hydrocarbons  which  have  been  isolated  from  petro- 
leum is  very  small.  The  old  procedures,  which  supplied  chemical  lit- 
erature with  a  formidable  array  of  names,  empirical  formulae  and 
boiling-points,  consisted  in  carefully  fractioning  a  quantity  of  petro- 
leum and  collecting  fractions  boiling  between  narrow  limits.  Formulae 
and  names  were  then  assigned  to  these  fractions  on  the  basis  of  com- 
bustion analyses  and  molecular  weight  determinations.  The  extremely 
careful  work  of  Young  shows  how  very  difficult  the  separation  of  only 
two  hydrocarbons  may  be  when  the  diffierence  in  boiling-points  is  as 
much  as  8°,  as  in  the  case  of  n.pentane  and  isopentane.  Young  and 
Thomas14  were  able  to  separate  n.pentane  and  isopentane  in  fairly 
pure  condition  only  after  thirteen  fractional  distillations  through  a 
very  efficient  dephlegmating  column,  and  Young  states  that  he  was  not 
able  to  isolate  pure  heptanes  from  light  petroleum  ether  by  fractional 
distillation.  He  regards  the  presence  of  n.hexane  and  isohexane  in 
American  and  Russian  petroleums  as  established,  but  the  presence 
of  other  hexanes  is  open  to  question.  Markownikow  was  able  to 
isolate  cyclohexane  and  methyl  cyclopentane  in  fairly  pure  state  from 
Baku  oil  by  a  combination  of  chemical  treatments  and  fractional  dis- 
tillation.15 In  the  course  of  his  work,  Young  showed  that  benzene  and 
hexane  form  a  constant  boiling  mixture  boiling  at  65°-66°.  Although 
the  distillation  of  two  closely  related  hydrocarbons,  for  example,  two 
members  of  the  series  CnH2n+2,  as  a  constant  boiling  mixture  is  very 
improbable  yet  it  is  a  possibility.  Also  owing  to  the  fact  that  the 
boiling-points  of  a  series  of  isomers  may  extend  over  a  wide  range, 
for  example  22°  in  the  case  of  the  hexanes,  it  is  evident  that  the  prob- 
lem of  isolating  pure  hydrocarbons  from  petroleum  distillates  is  practi- 
cally a  hopeless  one,  except  in  very  simple  cases  as  noted  above. 

Paraffine  hydrocarbons  are  produced  in  a  variety  of  biological  proc- 
esses. The  best  known  example  of  this  method  of  their  production  is 
methane,  the  name  "marsh  gas"  referring  to  its  formation  in  bogs 
where  cellulose  undergoes  anaerobic  fermentation.  The  amylobacteria 

14 J.  Am.  Chem.  Soc.  71,   440    (1897). 

"Aschan,  Ber.  SI,  1801  (1898).  Markownikow,  Ann.  SOI.  154  (1898);  Ber.  SO 
1532  (1897). 


THE  PARAFFINES  19 

of  van  Tiegham,16  evolve  methane  from  cellulose  and  in  this  fermenta- 
tion the  other  major  products  are  carbon  dioxide  and  the  simple  fatty 
acids.17  Whether  small  proportions  of  other  gaseous  hydrocarbons  are 
simultaneously  produced  has  not  been  determined.  As  regards  the 
theory  of  the  biological  origin  of  natural  gas  and  petroleum,  the  for- 
mation of  methane  from  buried  cellulose  material  is  capable  of  experi- 
mental duplication  but  this  cannot  yet  be  said  of  the  higher  homo- 
logues. 

Normal  heptane  has  been  obtained  from  the  "petroleum  nuts" 
Pittosporum  resiniferum  of  the  Philippines,18  from  the  oleoresin  of 
Pinus  sabinmna  and  the  wood  turpentine  of  Pinus  jeffreyi.19  The 
higher  paraffines  occur  in  small  quantity  in  many  essential  oils.  Com- 
mercial rose  oil  contains  sufficient  paraffine  or  "stearoptene"  to  sepa- 
rate in  large  crystals,  on  chilling.  This  crude  stearoptene  has  been 
separated  into  paraffines  melting  at  22°  and  40°  to  41°.  Heptacosane 
C27H56  and  hentriacontane  C31H64  occur  in  bees'  wax 20  and  the  latter 
hydrocarbon  also  occurs  in  the  resin  of  tobacco  and  the  leaves  of  Gym- 
nema  sylvestre,  Olea  europcea  or  the  European  olive,  an  African  vine 
Morinda  longiflora  and  Lippia  scaberrina21  According  to  Meyer  and 
Soyka  [Monatshefte,  84,  1159  (1913)],  candelilla  wax,  used  in  making 
phonograph  records,  contains  about  74  to  76  per  cent  of  do-triacontane, 
C32H66.  Small  quantities  of  crystalline  paraffine  wax  also  occur  in 
certain  eucalyptus  oils,  e.  g.,  Eucalyptus  paludosa  and  Eucalyptus 
smithii22  Pentatriacontane  C35H72  melting  at  74.5°-75°  occurs  in  the 
leaves  of  Eridictyon  calif  or  nicum23  Pentacontane,  C50H102,  has  been 
found  in  Lancashire  coal.  Altogether  several  tons  of  dark  colored  wax 
were  found  which  after  purification  and  decolorizing  melted  at  92.7°- 
93°  and  boiled  at  420°-422°  under  15  mm.  pressure.  This  hydro- 
carbon is  the  highest  homologue  of  the  paraffine  series  which  has  been 
found  occuring  naturally.24 

The  Character  and  Probable  Mode  of  Origin  of  Petroleums. 

The  development  of  the  petroleum  industry  had  its  beginnings 
almost  coincident  with  the  very  rapid  development  of  organic  chem- 

"Compt.   rend.   88,   205    (1879). 

"Lafar:  Tech.  Mykologie.     Vol.  III.  260   (1906). 

18  Bacon,  Philip  J.  Set.  4,  115   (1909). 

19  Schorger,  J.  Ind.  d  Eng.  Chem.  7,  24   (1915). 
"Schwalb,  Ann.  235,  110   (1886). 

21  Power  &  Tutin,  J.  Chem.  Soc.  91,  1916  (1907)  ;  93,  874   (1908). 

"Smith,  J.  Chem.  Abs.  106,  399   (1914). 

"Power  &  Tutin,  J.   Chem.  Soc.  Abs.  90,  885    (1906). 

M  Sinnatt  &  Barash,  Inst.  Min.  Eng.  1919,  Nov.  11. 


20        CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

istry.  The  petroleum  industry  was  largely  an  American  development 
but  extensive  research  in  organic  chemistry  was  for  long  carried  out 
almost  exclusively  in  Europe,  which  is  one  reason  for  the  comparative 
neglect  of  petroleum  research.  Also  during  these  earlier  years  few 
American  chemists  had  the  facilities  and  time  at  their  disposal  neces- 
sary for  research.  Most  American  chemists  of  that  period  were  an- 
alytical chemists,  with  the  result  that  the  earlier  investigations  of  pe- 
troleum consisted  in  laboriously  fractioning  petroleum  distillates  and 
christening  the  various  fractions  normal  undecane,  normal  dodecane, 
etc.,  etc.  With  the  exception  of  the  notable  pioneer  work  of  Mabery 
very  little  work  of  permanent  value  was  done  on  petroleum  in  America 
during  this  long  period. 

Young  demonstrated 26  the  presence  of  n .  pentane  and  isopentane 
in  petroleum,  also  the  presence  of  n.hexane  and  isohexane  and  n. hep- 
tane and  isoheptane,  but  considered  the  presence  of  isomeric  hex- 
anes  and  heptanes  as  probable  but  not  proven.  The  presence  of 
cyclo-hexane,  methyl-cyclopentane  27  and  a  limited  number  of  homo- 
logues  has  been  proven  in  the  case  of  light  naphtha  from  Baku  oil.  The 
isolation  of  a  fraction  having  a  constant  boiling-point  is  not  necessarily 
indicative  of  a  pure  single  hydrocarbon.  Two  isomers,  or  two  totally 
different  hydrocarbons  may  have  practically  identical  boiling-points.28 
Five  of  the  known  octanes  boil  within  the  range  114°-118°.  Con- 
stant boiling  mixtures  are  also  known,  the  separate  constituents  of 
which  may  have  quite  different  boiling-points.  For  example,  pure 
n.hexane  boils  at  68.95°  and  benzene  at  80.2°,  but  a  mixture  of  the 
two  containing  10  per  cent  benzene  boils  at  69°  and  a  mixture  contain- 
ing 27.3  per  cent  benzene  at  69.5°.  This  behavior  of  benzene  and 
hexane  explains  the  fact  that  on  nitrating  petroleum  fractions  contain- 
ing benzene,  the  fraction  yielding  the  most  dinitrobenzene  is  that 
boiling  at  60°-65°,  not  that  boiling  at  75°  to  85°.  For  a  similar  rea- 
son the  fraction  90°-100°  contains  more  toluene,  when  this  is  a  minor 
constituent,  than  the  fraction  distilling  at  105°-115°. 

All  petroleums  which  contain  paraffine  hydrocarbons  as  the  chief 
constituents  of  their  lighter  fractions,  as  the  Pennsylvania,  Mid-Conti- 
nent, and  light  Texas  crudes,  show  a  rapidly  increasing  per  cent  of 
naphthenes  as  the  boiling-point  rises  with  successive  fractions.  In  the 
light  lubricating  fractions  the  paraffine  hydrocarbons,  series  CnH911  2, 
seldom  exceeds  three  per  cent  and  after  their  removal  by  chilling,  re- 

28  J.  Chem.  8oc.  7S,  907   (1898). 

27  Young,  loc.  cit.;  Markownikow,  Ber.  SO,  1222  (1897). 

28  Jackson  &  Young,  J.  Chem.  Soc.  73,  926    (1898). 


THE  PARAFFINES  21 

suiting  in  the  paraffine  wax  of  commerce,  the  lubricating  oil  remaining 
is  practically  free  from  hydrocarbons  of  this  class.  Paraffine  wax  of 
commerce,  melting  ordinarily  from  48°  to  62°  C,  consists  chiefly  of  a 
mixture  of  hydrocarbons  of  23  to  28  carbon  atoms.  The  melting- 
points  and  boiling-points  of  some  of  the  definitely  known  paraffine 
hydrocarbons  are  given  in  the  following  table: 

BOILING-POINTS   OF  HYDROCARBONS   OF  THE  PARAFFINE  SERIES. 

Formula                     Name  Boiling-Point  "C. 

C«Hio              n.  butane  —  0.1 

isobutane  — 10.5 

n.  pentane  -f  36.3 

isopentane  27.95 

tetramethyl-methane  9.5 

n.  hexane  68.95 

2  methyl  pentane  62. 

3  methyl  pentane  64. 

22  dimethyl  butane  49.6  -49.7 

2.3         "           "  58.08 

CTHi4              n.  heptane  98.2  -98.5 

"                  2  methyl  hexane  89.9  -90.4 

"                  3       "           "  90.    -92. 

"                  trimethyl  methane  95.    -98. 

"                  22  dimethyl  pentane  78. 

"                  2.4         "               "  83.    -84. 

3.3         "               "  86.    -87. 

CsHis              n.  octane  125.8 

"                  2  methyl  heptane  116. 

"                  3       "           "  117.6 

MELTING-POINTS  AND  BOILING-POINTS  OF  HYDROCARBONS  OF  THE  PARAFFINE  SERIES. 

Formula                  Name  Boiling-Point  °C        Melting-Point  °C 

CsHw        4  methyl  heptane  118. 

2.4  dimethyl  hexane  109.8-110. 

2.5  "  109.2 

3.4  "             "  116.  -116.2 
diethyl-isopropyl  methane  114. 

2.2.3.3.tetramethyl  butane  106. -107.                     +103. 

n.nonane  149.5                               — 51. 

3  methyl  octane  142.4-143.4 

4  ethyl  heptane  138.  -139. 

2.5  dimethyl  heptane  133.  -137. 

2.6  "               "  132. 

ioHa        n.decane  173.                                 — 32. 

2.6  dimethyl  octane  156.5-158. 

2.7  "             "  159.6 

3.6        "             «  159.8-160.8 

n.undecane  194.5                               — 26.5 

n.dodecane  214.5                               —12. 

2.4.5.7  tetramethyl  octane  208.  -210. 

n.tridecane  234                                   —6.2 

n.tetradecane  252.5                                 +5.5 

n.pentadecane  270.5                               +10. 

n.hexadecane  287.5                               + 19.  -20. 

7.8  dimethyl  tetradecane  263. -265.                  below —30° 


22        CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

MELTING-POINTS  AND  BOILING-POINTS  OF  HYDROCARBONS  OF  THE  PARAFFINE  SERIES. 

Formula                Name  Boiling-Point  °C  Melting-Point  °C 

Ci7Hss       n.heptadecane  303.                                 +22.5 

n.octadecane  317.                                    28. 

n.nonadecane  330.                                    32. 

n.eikosane  205.  (15mm.)                     36.7 

n.heneikosane  215.  (15mm.)                     40.4 

n.dokosane  224.5  (15mm.)                     44.4 

n.trikosane  234.  (15mm.)                     47.7 

n.tetrakosane  240.  (15mm.)                     51.5 

n.hexakosane  ......                                 56.6 


Owing  to  the  fact  that  paraffine  wax  does  not  crystallize  readily  in 
well  formed  crystals,  even  from  crude  petroleums  which  are  free  from 
asphaltic  matter,  until  after  distillation,  it  has  been  supposed  that  the 
crystalline  paraffine  is  at  least  partly  derived  from  a  parent  substance, 
"proto-paraffine,"  which  breaks  up  during  distillation  and  thereby 
yields  the  freely  crystallizing  paraffine  wax.29  Rakuzin  30  has  shown 
that  crude  petroleums  contain  soft,  medium  and  hard  paraffines  of 
crystalline  structure.  Marcusson  31  slowly  distilled  ceresine  thereby 
decomposing  it  to  a  mixture  of  well  crystallized  paraffines  and  liquid 
hydrocarbons.  The  substance  known  to  the  refiners  as  amorphous  wax 
and  which  gives  much  trouble  to  the  wax  manufacturer,  may  possibly 
be  ordinary  paraffine,  whose  crystallization  is  interfered  with  by  col- 
loids, substances  capable  of  gelatinizing  on  chilling  or  may  in  fact  con- 
sist of  paraffine  derivatives,  "proto-paraffines,"  for  example,  naph- 
thenes  having  very  long  paraffine  side  chains  which  on  pyrolysis  yield 
crystalline  paraffine  wax  and  an  unsaturated  naphthene  or  its  polymers. 
A  better  method  of  separating  or  destroying  amorphous  wax  is  a 
problem  of  first  importance  to  the  refiners,  but  the  real  nature  of 
amorphous  wax  has  not  been  determined.  The  most  definite  informa- 
tion on  this  point  is  contained  in  a  recent  paper  by  Marcusson  32  who 
showed  that  amorphous  wax  is  probably  identical  with  ceresine  and 
there  is  considerable  evidence  that  ceresine  consists  of  a  mixture  of 
branched  chain  or  isoparaffines,  a  hypothesis  first  put  forward  by  Za- 
loziecki.33  Heretofore  ceresine  has  generally  been  regarded  as  a  mix- 
ture of  the  higher  normal  paraffine  homologues.  Marcusson  com- 
pared the  physical  and  chemical  properties  of  a  crystalline  paraffine 
and  a  refined  natural  ceresine  of  practically  identical  melting  points. 

»  Zaloziecki,  Z.  f.  angew.  Chem.  1888,  126. 

30  J.  Russ.  Phys.-Chem.  Soc.  1914,  1544;  J.  Chem.  Soc.  Abs.  106,  489   (1914). 

81  Chem,.  Ztg.  1915,  581,  613. 

"Ohem.   Ztg.   1915,  613. 

**Z.  angew.  Chem.  1888,  126. 


THE  PARAFFINES  23 

Paraffine  Ceresine 

Melting-point    56.5°    -60.5°  57.5°    -60.1° 

Solidifying-point    59.2°  59° 

Sp.  Gr.  at  15°   0.885  0.917 

Sp.  Gr.  at  60°   0.781  0.798 

Mol.  Wt 330.  420. 

Paraffine  is  harder  than  ceresine  in  penetration  tests,  is  markedly 
more  soluble  and  is  less  viscous  than  ceresine  at  70°.  Paraffine  is  only 
slightly  attacked  by  fuming  sulfuric  acid,  33%  S03,  at  ordinary  tem- 
peratures, but  ceresine  is  energetically  attacked.  The  action  of  nitric 
acid  is  also  more  energetic  on  ceresine.  On  dissolving  paraffine  in  hot 
mineral  oil  and  then  cooling,  the  paraffine  crystallizes  out  but  with 
ceresine,  under  the  same  conditions,  a  vaseline-like  deposit  is  obtained. 
Marcusson  has  examined  the  distillation  products  of  ceresine  and  the 
oily  product  consists  of  a  mixture  of  saturated  hydrocarbons  and  de- 
fines of  low  molecular  weight.  No  evidence  of  the  presence  of  naph- 
thenes  was  obtained. 

The  formation  of  branched  chain  hydrocarbons  or  so-called  iso- 
paraffines  may  possibly  be  explained  by  the  decomposition  of  montan 
wax,  which  as  shown  by  Meyer  and  Brod  34  consists  chiefly  of  an  acid, 
C28H5602,  and  a  solid  alcoholic  wax.  This  acid  of  montan  wax  is  not 
a  normal  chain  fatty  acid  but  a  branched  chain  compound. 

Paraffine  is  formed  during  the  distillation  of  asphalt  base  oils  by 
the  decomposition  of  the  asphaltic  matter.  This  is  in  accord  with  the 
observation  that  large  amounts  of  crystalline  paraffine  are  contained 
in  shale  oil,  the  wax  not  being  present  as  such  in  the  original  shale 
but  formed  by  the  decomposition  of  the  complex  kerogen  of  the  shale ; 
also  the  distillate  obtained  by  the  low  temperature  distillation  of  coals 
rich  in  volatile  matter  contains  crystalline  paraffine,  which  is  not  pres- 
ent as  such  in  the  original  coal. 

In  addition  to  the  problem  of  separating  simple  mixtures  of  hydro- 
carbons by  fractional  distillation  and  the  separation  of  paraffine  wax 
by  chilling  and  crystallizing,  it  should  be  noted  that  other  special  meth- 
ods must  be  resorted  to,  to  isolate  substances  of  a  particular  class  from 
a  particular  petroleum.  Petroleums  contain  varying  proportions  of 
the  following  classes  of  substances,  all  of  which  are  very  imperfectly 
known  chemically: 

(1)  Paraffine  hydrocarbons,  liquid  and  solid,  series  CnH2n+a. 

(2)  Saturated    monocyclic    or    napththene    hydrocarbons,    empirical    formula 

cya*,. 

(3)  Saturated  polycyclic  hydrocarbons,  empirical  formulae. 

v^n-H^n — 2,     OnHzn — 4,     OnHzn — 6}    CtC. 

14  Monatshefte,  1913,  1153. 


24        CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

(4)  Benzenoid  hydrocarbons  and  derivatives. 

(5)  Unsaturated  hydrocarbons.     (Present  in  distillates  but  probably  not  pres- 

ent in  most  crude  petroleums.) 

(6)  Asphaltic  matter. 

(7)  Sulfur  derivatives. 

(8)  Nitrogenous  substances. 

(9)  Organic  acids  ("naphthenic"  acids,  not  of  the  fatty  acid  series). 

(10)     Coloring  matter  and  fluorescent  substances  (these  substances  may  belong 
to  other  classes  enumerated  above). 

The  majority  of  American  petroleums  yield  gasolenes  and  kero- 
senes consisting  chiefly  of  paraffine  hydrocarbons.  All  American  pe- 
troleums which  contain  large  proportions  of  these  lighter  distillates, 
such  as  the  light  Appalachian,  mid-Continent  and  northern  Texas 
crudes,  yield  gasolene  and  kerosene  of  this  character.  Low  boiling 
distillates  consisting  of  cyclic  hydrocarbons  or  naphthenes  are  usually 
derived  from  heavier  crudes  yielding  very  little  of  the  lighter  dis- 
tillates for  example,  the  heavy  California  and  the  Jennings,  Louis- 
iana crude  from  which  Coates  35  has  isolated  dicyclic  hydrocarbons 
C10H18  to  C13H24  and  the  Russian  and  Galician  oils  from  which  cyclo- 
pentane,  cyclohexane,  and  a  series  of  their  derivatives  has  been  iso- 
lated.36 The  determination  of  the  structure  of  these  naphthenes, 
coupled  with  the  difficulty  of  their  isolation  in  a  state  of  purity,  is  a 
task  as  difficult  as  any  in  organic  chemistry,  and  it  is  doubtful  if  very 
much  light  will  be  thrown  on  their  constitution  until  it  is  shown  that 
chemical  methods  of  utilization  may  lead  to  the  extraction  of  greater 
profits,  than  are  now  obtained,  though  it  is  easily  conceivable  that  the 
latter  result  cannot  be  arrived  at  without  the  former. 

Beilstein  and  Kurbatow  37  showed  that  the  more  volatile  hydro- 
carbons of  Russian  petroleum  possessed  the  empirical  formula  CnH2n, 
exhibited  none  of  the  reactions  of  olefines  and  in  their  general  chemical 
behavior  resembled  the  hydrocarbons  of  the  methane  series.  Two  hy- 
drocarbons of  the  formula  C6H12,  one  38  boiling  at  72°  and  the  other  39 
at  80°  were  isolated.  Cyclohexane,  prepared  by  Baeyer,  proved  iden- 
tical with  the  latter  hydrocarbon  from  Russian  petroleum  and  it  was 
then  shown  that  the  isomeric  hydrocarbon  was  methyl  cyclopentane. 
Markownikow  obtained  evidence  of  the  presence  of  cycloheptane  in  the 
fraction  boiling  at  115°-120°  of  a  Caucasian  oil.  With  the  exception 
of  the  bicyclic  decahydronaphthalene  isolated  by  Ross  and  Leather 40 

88  J.   Am.    Chem.   Soc.   28,  384    (1906). 
*«Ann.  301,  154  (1898)  ;  302,  37   (1898)  ; 
87  Ber.  IS,  1818,  2028  (1880).    307,  342  (1899). 
"Kishner,  J.  Ritss.  Phys.-Chem.  Soc.  20,  118   (1890). 
"Markownikow,  Ann.  802,  1    (1898). 

*»  Analyst  31,  284  (1906)  ;  This  hydrocarbon  is  now  made  commercially  by  the 
catalytic  hydrogenation  of  naphthalene. 


THE  PARAFF1NES 


25 


from  Borneo  petroleum  the  structure  of  the  higher  boiling  naphthenes 
is  largely  a  matter  of  conjecture. 

PHYSICAL  PROPERTIES  OF  SOME  SATURATED  CYCLIC  HYDROCARBONS. 


Empirical  Formula 
C^Hs 


04x17.0x13 


C^.CH, 

r.C2H5 


C3H3.(CH3)S 


Name 
Cyclopropane  tt 

Cyclobutane  ** 

Methyl  cyclopropane41 

*Cyclopentane  ** 

Methyl  cyclobutane  ** 

1.1  dimethyl  cyclopropane4* 

'Cyclohexane  4T 
*Methyl  cyclopentane  ** 
Ethyl  cyclobutane  *" 

1.2.3.  trimethyl  cyclopropane 
1.1.2.        " 

Cycloheptane  (suberane)  M 
*Methyl  cyclohexane5* 

1.1  dimethyl  cyclopentane  ra 

1.2  "  "  ° 
i-1.3    " 

Cyclo-octane  M 

Ethyl  cyclohexane  M»  M 

1  .  1  dimethyl  cyclohexane  M 

1.2  dimethyl  cyclohexane  n 


"Ladenburg  &  Kriigel,  Per.  S2,  1821   (1899). 

«  Willstatter  &  Bruce,  Ber.  40,  3979   (1907). 

«Demjanow,  Ber.  28,  21   (1895). 

**  Markownikow,  Ann.  327,  59    (1903). 

*5Perkin  &  Colman,  J.  CJiem.  Soc.  53,  201   (1888). 

"Gustavson  &  Popper,  J.  pr.  Chem.   (2),  58,  458  (1898). 

"Perkin  &  Freer,  J.  Chem.  Soc.  53,  203    (1895). 

"Zelinsky  &  Gutt,  Ber.  41,  2431    (1908). 

«Zelinsky  &  Zelikow,  Ber.  S),,  2857    (1901). 

MWillstatter  &  Kametaka,  Ber.  41,  1480   (1908). 

61  Sabatier  &   Senderens,   Compt.  rend.  132,  566    (1901). 

62Kishner,  CJiem.  Cent.  1908,  II,  1860. 

"Zelinsky  &  Rudsky,  Ber.  2.9,  405   (1896). 

M  Willstatter  &  Veraguth,  Ber.  40,  968  (1907). 

65  Kursanoff,  Ber.  32,  2973   (1899). 

MCrossley  &  Renouf,  J.  Chem.  Soc.  87,  1498  (1905). 

"Sabatier  &  Mailhe,  Compt.  rend.  141,  20   (1905). 


C8H1 


Boeing-Point  °C 

Sp.  Gr. 

35. 

n° 

11.  -  12. 

0.7038^0 

4.  -    5. 

49. 

0.7635^ 

39.  -  42. 

21. 

81. 

0.7934  ^p- 

70.  -  71. 

**10° 

72.2-  72.5 

0.7540^ 

65.  -  67. 

0.6946^ 

57.  -  59. 

0.6832^- 

118. 

0.8275^1 

18° 

100.  -101. 

0.7662^- 
4 

88. 

0.7547$! 

92.  -  93. 

100 

0.7581^ 

94° 

93. 

0.7410|L 

145.3-146.3 
M.-Pt.  11.5 

0-850  51 

132.  -133. 

0.7913^ 

120. 

n° 

124. 

0.8002^ 

26        CHEMISTRY  OF  THE  NON-BENZEN01D  HYDROCARBONS 

PHYSICAL  PROPERTIES  OF  SOME  SATURATED  CYCLIC  HYDROCARBONS. 
Name  Empirical  Formula        Boiling-Point  °C       Sp.  Gr. 

1.3  dimethyl  cyclohexane  "  "  118.  0.7869  ^o 

1.4  «  «  w  «  119.  0.7861  5! 
1  methyl-3-ethyl  cyclopentane  B8          CBH8<S]^3                 120.5-121.          0.7669^ 

U2X15  4 


1.1.2  trimethyl  cyclopentane09  CBH7(CH3)3  113.  -113.5        0.7847  ^ 

Cyclononane  w  ........  170.  -172. 

Aromatic,  or  benzenoid,  hydrocarbons  have  been  found,  usually  in 
very  subordinate  proportions,  in  all  petroleums  which  have  been  care- 
fully investigated.  The  per  cent  by  volume  of  benzenoid  hydrocarbons 
present,  as  reported,  is  often  too  high  particularly  when  nitration  meth- 
ods have  been  employed.  This  error  is  due  to  the  relative  ease  with 
which  non-benzenoid  hydrocarbons  are  nitrated.  Thus  Edeleanu  and 
Gane61  report  a  yield  of  41%  nitro  products  from  gas  oil  from  Penn- 
sylvania oil,  a  figure  obviously  far  too  high  to  accord  with  the  em- 
pirical combustion  analysis  and  well  known  behavior  of  this  oil  to 
consider  this  figure  as  an  indication  of  the  proportion  of  benzene  de- 
rivatives present.  However  in  the  case  of  the  lighter  distillates  the 
crystalline  nitrated  products  can  often  be  isolated  and  positively  iden- 
tified. The  presence  of  benzene  has  been  shown  in  petroleums  of  va- 
rious origins  and  Mabery  62  had  no  difficulty  in  isolating  naphthalene 
from  a  California  oil  by  fractional  distillation,  the  fraction  boiling 
at  220°-222°  finally  solidifying  in  the  condenser.  According  to  Jones 
and  Wootton  63  Borneo  petroleum  contains  6  to  7  per  cent  hydrocarbons 
of  the  naphthalene  series.  This  oil  contains  mono  and  dimethyl  deriva- 
tives of  naphthalene.  Brooks  and  Humphrey  64  found  small  quantities 
of  benzene  and  toluene  in  gasolene  made  by  distilling  the  heavy  high 
boiling  residue  of  Oklahoma  oil  at  about  420°  C.  and  under  a  pressure 
of  about  100  pounds.  Inasmuch  as  practically  no  hydrogen  is  present 
in  the  gases  formed  in  the  process  they  suggested  that  these  small  per- 
centages of  benzene  and  its  simpler  homologues  were  formed  as  de- 

"Zelinsky,  Ber.  35,  2679   (1902). 

MCrossley  &  Renouf,  J.  Chem.  Soc.  89,  33    (1896). 

«°Zelinsky,  Ber.  W,  3279    (1907). 

81  Rev.  gen.  Petrol.  1910,  393. 

92  J.  Soc.  Chem.  Ind.  19,  52  (1900). 

98  J.  Chem.  Soc.  91,  1146   (1907). 

8*  J.  Am.  Chem.  Soc.  S8,  393  (1916)  ;  The  formation  of  benzene  and  toluene  at 
much  higher  temperatures,  as  in  the  Hall  or  Rittman  process,  is  an  altogether  dif- 
ferent matter.  In  this  latter  process  hydrogen  is  always  an  important  constituent  in 
the  evolved  gases  and  it  makes  little  difference  what  petroleum  oil  fraction  is  employed, 
in  fact  fairly  pure  pentane  or  hexane  or  paraffine  wax  will  yield  substantial  quantities 
of  benzenoid  hydrocarbon  under  these  conditions.  Cf.  Egloff  &  Twomey,  J.  Phys. 
Chem.  W,  515  (1916)  ;  Egloff,  Met.  &  Chem.  Eng.  15,  692  (1916). 


THE  PARAFFINES  27 

composition  products  of  high  boiling  benzene  derivatives  which  were 
present  in  the  original  petroleum,  rather  than  by  the  dehydrogenation 
of  saturated  cyclic  hydrocarbons. 

Petroleums  are  normally  free  from  olefinic  hydrocarbons.  Such  hy- 
drocarbons are,  however,  invariably  present  in  petroleum  distillates. 
LeBel 65  found  amylene  and  two  isomeric  hexenes  in  the  light  distillate 
from  a  petroleum  from  Pechelbronn,  but  regarded  them  as  decompo- 
sition products  formed  during  distillation  of  the  crude  oil.  Balbiano 
and  Paolini 66  detected  olefines  in  an  American  kerosene  (by  the  for- 
mation of  a  precipitate  with  mercuric  acetate),  and  Mabery  and 
Quayle 67  reported  hexenes,  heptenes  and  octenes  in  a  distillate  from  a 
Canadian  petroleum.  But  in  so  far  as  the  presence  of  olefines  in  crude 
petroleum  is  concerned,  a  clear  demonstration  of  their  presence  is  lack- 
ing, except  in  the  case  of  a  sample  examined  by  Zaloziecki 6T  and  said 
to  have  come  from  Java.  The  occurrence  of  terpene  like  hydrocarbons 
has  sometimes  been  reported  but  Coates  has  shown  that  the  turpentine- 
like  odor  of  the  Jennings,  Louisiana,  oil  is  due  to  saturated  bicyclic  hy- 
drocarbons and  that  this  petroleum  contains  no  olefines.  The  pres- 
ence of  olefines  cannot  be  demonstrated  or  quantitatively  measured  by 
the  usual  iodine  or  bromine  absorption  methods  owing  to  substitution 
reactions  taking  place.  These  methods  invariably  give  too  high  re- 
sults in  the  case  of  pyrolytic  distillates. 

The  relative  ease  with  which  olefines  are  polymerized  by  fuller's 
earth  and  similar  substances  may  explain  the  absence  of  these  unsatu- 
rated  hydrocarbons  in  petroleums.  Until  an  authentic  crude  petroleum 
can  by  proper  experimental  methods  be  shown  to  contain  them,  the 
statement  that  olefinic  hydrocarbons  are  not  present  in  crude  petro- 
leums seems  amply  justified. 

Very  little  is  known  regarding  the  sulfur  compounds  contained  in 
crude  petroleums  and  distillates.  The  refiner  is  concerned  only  with 
deodorizing  the  distillates  and  the  chemical  character  of  the  sulfur 
derivatives  is  of  no  interest  to  him.  The  well  known  method  of  Frasch, 
consisting  in  the  desulfurizing  of  oil  by  treatment  with  copper  oxide, 
was  developed  particularly  for  oils  from  Canada  and  the  Lima-In- 
diana field  and  Mabery  and  Quayle  68  have  investigated  the  sulfur 
compounds  of  the  Canadian  oil  and  discovered  what  is  apparently  a 
new  series  of  organic  compounds  of  sulfur.  By  distilling  the  oil  in 

"Compt.  rend.  75,  267   (1872)  ;  81,  967    (1875). 

*  Chem.  Ztg.  1901,  932. 

"Naphtha,  1900,  222. 

"Aw.   Chem.  J.  35,  404    (1906). 


28        CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

vacuo  and  treating  the  distillates  with  alcoholic  mercuric  chloride  they 
obtained  precipitates  of  the  sulfur  compounds  which  were  then  decom- 
posed by  hydrogen  sulfide.  In  empirical  composition  these  substances 
are  identical  with  hydrothiophenes  (which  have  not  been  made  syn- 
thetically), and  Mabery  has  designated  them  as  thiophanes.  They  are 
oxidized  by  permanganate  or  chromic  acid  to  sulfones,  thick,  viscous 
oils  of  slight,  rather  pleasant  odors,  and  they  combine  with  ethyl  iodide 
to  form  products  of  the  empirical  composition  CnH2nS.C2H5I,  the  iodine 
being  replaceable  by  hydroxyl,  by  means  of  silver  oxide,  to  give  basic 
substances.  The  thiophanes  are  comparatively  stable.  Mexican  pe- 
troleums contain  as  much  as  7.5%  sulfur  but  no  differentiation  between 
dissolved  or  suspended  free  sulfur  and  combined  sulfur  has  been  made. 
Mexican  and  many  of  the  Gulf  coast  oils  contain  free  sulfur  69  and 
on  distillation  hydrogen  sulfide  is  evolved.  Organic  bases  such  as 
aniline,  pyridine  and  quinoline,  and  also  ammonia  react  with  many, 
perhaps  all,  of  the  sulfur  compounds  contained  in  petroleums,  pyri- 
dine being  said  to  "catalyse"  the  evolution  of  hydrogen  sulfide.  The 
desulfurizing  of  petroleum  by  heating  in  the  presence  of  free  ammonia, 
hydrogen  sulfide  being  formed,  has  been  proposed  by  F.  M.  Perkin.70 
By  retorting  certain  shales,  distillates  rich  in  sulfur  are  obtained 
which  may  be  sulfonated  by  concentrated  sulfuric  acid  and  the  product, 
in  the  form  of  water  soluble  ammonium  salts,  is  the  material  known 
in  pharmacy  and  medicine  as  "ichthyol,"  so  named  because  the  shales 
in  Austria  from  which  the  ichtriyol  oil  was  first  derived  are  rich  in 
fossil  fish  remains.  The  product  is  a  complex  mixture  of  substances, 
of  variable  composition  and  practically  nothing  is  known  as  to  the 
chemical  nature  or  structure  of  the  sulfur  derivatives  in  the  original 
distillate.  Other  shales  yield  similar  distillates,  for  example: 

Per  cent 
Oil  from  shale  at,  C.  H.  N.  O.  S. 

St.  Champ,  France 71 77.3  9.2  0.37  1.14  11.99 

Tuscany    69.5  8.7  2.27          11.6  7.79 

In  preparing  ichthyol,  the  crude  distillate  is  sulfonated  by  treating 
with  ordinary  concentrated  sulfuric  acid,  slightly  diluted  with  water  or 
brine  and  the  unsulfonated  oil  extracted  by  petroleum  ether  and  the 
sulfonic  acids,  neutralized'  by  ammonia.  The  commercial  product  al- 
ways contains  ammonium  sulfate  on  account  of  the  practical  impos- 
sibility of  completely  removing  the  excess  sulfuric  acid.72  The  crude 

••Richardson,  J.  8oc.  Chem.  Ind.  21,  316  (1902). 
"Chem.  Trade  J.  50,  251   (1917). 

"Demesse  &  Reaubourg,  Bui.  Soc.  cMm.  15,  625   (1914). 
"Puckner,  Lab.  Rep.  Am.  Med.  Assn.  5,  110. 


THE  PARAFFINES  29 

oil  contains,  in  addition,  to  sulfur  compounds,  phenols  and  organic 
acids.73 

The  occurrence  of  nitrogen  bases  in  petroleum  is  by  no  means  rare 
and  the  percentage  of  such  bases  in  many  crude  petroleums  is  relatively 
large.  Ordinarily  the  proportion  of  nitrogen  in  petroleum  does  not 
exceed  1.5  per  cent  but  an  Algerian  oil  is  reported  as  having  2.17  per 
cent  and  a  Japanese  2.25  per  cent.  The  highest  per  cent  of  nitrogen 
thus  far  reported  is  2.39  per  cent,  found  in  a  Californian  oil.  This 
means  that  probably  20  per  cent  of  this  oil  consists  of  nitrogen  bases. 
Very  little  is  known  as  to  the  character  of  these  bases.  The  separation 
of  definite  substances  by  fractional  distillation  of  the  bases  recovered 
from  the  acid  washings  of  the  oil  has  not  been  successful.  They  form 
precipitates  from  acid  solutions  with  platinum,  palladium,  mercuric, 
cadmium  and  ferric  chlorides,  potassium  dichromate,  ferro  and  ferri- 
cyanides  and  picric  and  oxalic  acids.  By  oxidation  with  alkaline  per- 
manganate in  alkaline  solution  the  nitrogen  is  evolved  partly  as  free 
nitrogen  and  partly  as  ammonia.  Oxidation  by  chromic  acid  has  led 
to  no  definite  results.  Decomposition  by  the  method  of  exhaustive 
methylation  does  not  appear  to  have  been  given  a  fair  trial;  ethyl 
iodide  combines  with  these  bases  when  heated  together  in  a  sealed  tube. 
The  bases  are  weakly  basic.  In  1900  Mabery 7*  concluded  that  the 
nitrogen  bases  in  California  petroleum  consisted  of  a  mixture  of  more 
or  less  hydrogenated  quinolines.  Recently  Mabery  has  returned  to  the 
problem  and  in  a  recent  paper,  with  L.  G.  Wesson,75  has  shown  that  by 
careful  oxidation  with  potassium  permanganate,  the  various  fractions, 
derived  from  the  crude  mixture  of  bases  yield  pyridine  pentacarboxylic 
acid  and  methyl  pyridine  tetracarboxylic  acid.  No  higher  fatty  acids 
were  observed  among  the  oxidation  products.  By  oxidizing  with 
chromic  acid  and  subjecting  the  calcium  salts  of  the  acids  thus 
formed  to  dry  distillation,  p-methylquinoline  is  produced.  Mabery 
and  Wesson  conclude  that  the  organic  bases  of  California  petroleum 
consist  mainly  of  an  indefinite  mixture  of  alkylated  quinolines  or  iso- 
quinolenes,  the  rings  containing  the  nitrogen  being  completely  alkyl- 
ated by  small  alkyl  groups. 

Origin  of  Petroleum. 

The  great  preponderance  of  opinion  among  geologists  and  chemists 
is  in  favor  of  the  theories  of  the  origin  of  petroleum  from  organic  rather 

"Scheibler,  Ber.  48,  1815   (1915). 
74  J.  Soc.  Chem.  Ind.  19,  505    (1900). 
™J.  Am.  Chem.  Soc.  &,  1014    (1920). 


30        CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

than  inorganic  sources.  [In  view  of  this  fact  a  discussion  of  the  theories 
of  inorganic  origin  will  be  omitted  here  but  good  reviews  of  this  phase 
of  the  subject  are  available  in  many  standard  works.76]  A  great  deal 
has  been  written  on  this  theme  but  experimental  evidence  is  almost  al- 
together lacking.  The  chief  evidence  is  of  an  altogether  different  na- 
ture, namely  geological  and  geochemical  on  the  one  hand  and  the  gen- 
eral chemical  character  of  petroleums  on  the  other.  The  question  is 
one  that  hardly  lends  itself  to  direct  experimental  study. 

Both  animal  and  vegetable  matter  have  probably  contributed  to  the 
formation  of  petroleums  and  natural  gases  and  decay  of  such  organic 
rnatter  appears  to  be  easily  adequate  to  the  formation  of  the  quantities 
of  oil  and  gas  which  are  found  buried  in  the  strata.  Geologists  T7  have 
called  attention  to  the  fact  that  petroleum  is  very  widely  dissemi- 
nated through  many  limestone  and  sandstone  strata  of  enormous  thick- 
ness and  area.  Thus  it  has  been  estimated  that  in  the  limestone  of 
Chicago,  which  has  a  thickness  of  about  35  feet,  there  are  over  7,000,- 
000  barrels  of  oil  in  each  square  mile  of  this  stratum. 

The  deposits  of  petroleum  at  Baku  and  the  surrounding  territory 
are,  nearly  all,  in  Tertiary  formations,  and  the  menilite  shale  in  which 
the  petroleum  occurs  is  certainly  of  marine  origin.  It  has  been  esti- 
mated that  if  the  annual  deposition  of  fish  remains  in  these  rocks  were 
equivalent  to  the  annual  catch  in  the  fisheries  of  northern  Europe,  and 
that  only  50  per  cent  of  the  oil  in  these  remains  were  converted  into 
petroleum,  a  period  of  about  2500  years  would  suffice  for  the  entire 
petroleum  accumulations  in  the  Carpathian  area.  Engler  has  pointed 
out  that  both  animal  and  vegetable  remains  may  have  contributed  to 
the  formation  of  petroleum  and  Kraemer  and  Spilker  78  have  pointed 
out  that  certain  algae  contain  droplets  of  oil  in  their  cells. 

Petroleums  may  be  very  much  altered  by  filtration  through  fine 
sand  or  other  fine  material  as  has  been  shown  experimentally  by  the 
work  of  Day,  Gilpin  and  Kramm  and  others,  the  more  fluid  and  vola- 
tile hydrocarbons  being  gradually  separated  from  the  more  complex 
and  less  volatile  constituents.  This  undoubtedly  accounts  for  the  char- 
acter of  certain  crude  petroleums  which  are  very  slightly  colored  and 
sometimes  contain  upwards  of  30%  of  gasolene.  In  the  accumulation 
of  such  oils  in  pools,  the  oil  must. in  many  cases  have  traveled  long 
distances  through  the  porous  rock. 

'•Data  of  Geo-Chemistry  by  F.  W.  Clark,  Bulletin  695,  U.  S.  Geological  Survey, 
Washington,  1920. 

77  Orton,  Ohio  Geological  Survey,  First  Annual  Report  1870,  and  Hunt :  Chemical 
and  Geological  Essays  1875,  p.  168. 

™Ber.  35,  1212    (1901). 


THE  PARAFFINES  31 

Practically  all  petroleums  which  have  been  investigated  give  dis- 
tillates which  show  slight  optical  activity.  Inasmuch  as  no  synthetic 
process,  such  as  the  formation  of  hydrocarbons  from  carbides  and  the 
like,  yields  optically  active  material,  the  presence  of  optically  active 
substances  in  petroleum  is  considered  to  be  one  of  the  strongest  argu- 
ments in  support  of  the  organic  origin  of  petroleum.  Although  pure 
fatty  glycerides  are  not  optically  active,  natural  fats  and  oils  contain 
small  quantities  of  cholesterol,  phytosterol,  protein  decomposition  prod- 
ucts and  the  like  which  are  optically  active.  When  oils  containing 
cholesterol  or  phytosterol  are  subjected  to  distillation  under  pressure 
the  maximum  optical  activity  is  observed  in  the  same  fractions,  with 
respect  to  boiling  point,  as  is  the  case  with  petroleum  distillates.79 

It  is  not  too  much  to  expect  that  further  study  will  reveal  the 
chemical  history  of  the  formation  of  petroleum  as  clearly  as  the  for- 
mation of  coal  is  revealed  in  the  series  of  changes  through  peat,  the 
lignites,  bituminous  coals  and  anthracite.  This  information  will  un- 
doubtedly be  obtained  through  a  study  of  superficial  or  recently  buried 
deposits  rather  than  by  experimental  work  seeking  to  produce  the  re- 
sults by  laboratory  methods.  Phillips  observed  the  anaerobic  fermen- 
tation of  sea  weeds  in  an  apparatus  which  was  observed  over  a  period 
of  two  and  a  half  years.  At  first  a  little  methane  together  with  larger 
quantities  of  carbon  dioxide,  hydrogen  and  nitrogen  were  evolved  but 
toward  the  end  of  the  experiment  the  evolved  gas  consisted  chiefly  of 
methane. 

In  addition  to  the  geological  evidence  of  the  organic  origin  of  pe- 
troleum, a  wealth  of  evidence  is  found  in  the  chemical  character  of  pe- 
troleums themselves,  particularly  the  optically  active  constituents, 
naphthenic  acids,  nitrogen  and  sulfur  derivatives. 

A  great  der.l  of  the  experimental  investigations  which  have  given 
support  to  the  organic  theory  have  been  carried  out  by  Engler  and 
his  students.80  Engler  believes  that  in  the  anaerobic  decay  of  marine 
animal  remains  the  fatty  oils,  being  more  resistant  to  putrefactive 
changes,  remain  entangled  in  the  marine  sediments  long  after  the  pro- 
teins and  other  organic  constituents  have  been  lost  by  putrefactive  de- 
cay. He  has  shown  that  when  fish  oil  is  heated  or  distilled  under  pres- 
sure, good  yields  of  a  liquid  hydrocarbon  mixture  are  obtained,  which 

n  Walden,  Chem.  Ztg.  SO,  391,  1155,  1168  (1906)  ;  Rakuzin,  8th  Int.  Cong.  Appl. 
Chem.  25,  721 ;  Ber.  tf,  1211,  1640,  4675  (1908)  ;  Marcosson,  Chem.  Ztg.  32,  377,  391 
(1908)  ;  Ubbelohde,  Ber.  1,2,  3242  (1909)  ;  48,  608  (1910). 

80  Ber.  21,  1816  (1888)  ;  26,  1449  (1893)  ;  SO,  2365  (1897)  ;  Z.  f.  angew.  Chem. 
1908,  1585  ;  Ber.  J#,  4610,  4613,  4620  (1909)  ;  43,  388,  954  (1910)  ;  Z.  f.  angew.  Chem. 
1912,  4. 


32        CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

very  greatly  resembles  crude  petroleum  in  its  physical  characteristics 
and  chemical  composition.  Such  distillates  have  a  marked  green  fluor- 
escence and  in  the  lighter  fractions,  obtained  by  fractional  distillation, 
n.pentane,  n.hexane,  n. heptane,  n. octane,  and  nonane  were  identified. 
By  chilling  the  fraction  boiling  above  300°  crystalline  paraffine,  melt- 
ing-point 49°  to  51°,  was  obtained  and  also  a  viscous  fraction  closely 
resembling  lubricating  oil  was  isolated.  These  distillates  obtained  by 
Engler  contained  notable  percentages  of  unsaturated  hydrocarbons, 
thus  differing  from  crude  petroleum  but  this  difference  is  readily  un- 
derstood, in  view  of  the  experimental  demonstration  of  Gurwitsch  81 
that  fuller's  earth  rapidly  polymerizes  unsaturated  hydrocarbons.  Thus 
at  ordinary  temperatures  amylene  is  85%  polymerized  in  two  days. 
Engler's  distillates  contain  small  quantities  of  aromatic  hydrocarbons, 
benzene,  toluene  and  xylene  being  identified  by  their  nitro  compounds, 
these  distillates  resembling  crude  petroleums  in  this  respect.  Very 
similar  results  were  obtained  by  distilling  animal  and  vegetable  oils 
and  fats  under  pressure. 

Although  the  strata  in  which  petroleum  oils  occur  are  never  found 
at  sufficient  depth  to  be  subjected  to  the  temperatures  employed  by 
Engler  and  in  most  cases  have  not  been  subjected  to  volcanic  intrusions, 
marked  folding  of  the  strata  or  other  sources  of  heat,  Engler,  neverthe- 
less, supposes  that  these  same  destructive  changes  which  he  effects  by 
pressure  distillation  may  be  effected  in  Nature  at  very  much  lower 
temperatures  during  the  long  course  of  geologic  time.  Though  little 
is  definitely  known  in  regard  to  the  substances  in  petroleum  which  con- 
tain oxygen  and  sulfur,  the  mere  presence  of  these  substances  is  indi- 
cative of  an  organic  rather  than  an  inorganic  origin.  Mabery  has 
shown  that  the  nitrogenous  constituents  of  California  petroleum  are 
hydrogenated  quinolines.82 

Asphaltic  matter  is  undoubtedly  formed  by  oxidation,  which  process 
readily  explains  such  deposits  as  that  of  Trinidad  Island  and  such  a 
process  is  closely  duplicated  in  the  well-known  process  of  Byerley  and 
Mabery  of  blowing  air  through  the  heavy  residuum  left  in  the  stills 
after  the  more  volatile  fractions  have  been  distilled  from  crude  pe- 
troleums. 

As  regards  sulfur  compounds  these  have  been  ascribed  to  the  de- 
composition of  organic  remains  and  it  is  noteworthy  that  certain  oils 
rich  in  sulfur  are  associated  with  shales  containing  abundant  fossil  re- 

81 J.  Rusa.  Phya.-Ohem.  Soc.  tf,  827   (1915)  ;  J.  Chem.  SQC.  1915,  I,  933. 
82  J.  Am.  Uhem.  Soc.  42,  1014   (1920). 


THE  PARAFFINES  33 

mains  of  fish.  This  is  particularly  true  of  the  Austrian  deposit  from 
which  the  well-known  pharmaceutically  valuable  "ichthyol"  is  de- 
rived. These  sulfur  compounds,  however,  may  have  been  formed  in  a 
very  different  manner.  It  is  well  known,  for  example,  that  sulfates 
can  be  reduced  by  organic  matter  or  by  anaerobic  fermentation  with 
the  formation  of  sulfur.  Sulfur  in  very  large  masses  is  often  found 
associated  with  petroleum  in  the  American  Gulf  Coast  region  and  its 
formation  is  perhaps  best  accounted  for  in  this  manner.  It  is  also  well 
known  that  free  sulfur  reacts  with  hydrocarbons  with  relative  ease. 
The  direct  addition  of  sulfur  to  unsaturated  hydrocarbons  has  been 
shown  by  Erdmann.  Reaction  with  saturated  hydrocarbons,  paraffine 
for  example,  can  be  effected  at  very  moderate  temperatures.  In  the 
latter  case,  hydrogen  sulfide  is  evolved,  and  this  gas  accompanies  the 
Gulf  Coast  petroleums  sometimes  in  very  large  quantities. 

The  Formation  of  the  Paraffines. 

Decomposition  of  a  wide  variety  of  organic  substances  by  heat 
yields  paraffine  hydrocarbons  among  the  products  so  formed.  Methane 
is  an  important  constituent  of  retort  coal  gas  (30  to  40%),  by-product 
coke  oven  gas,  oil  gas  and  the  like.  The  per  cent  of  methane  contained 
in  such  gases  depends  upon  many  factors,  for  example  temperature, 
the  duration  of  the  heating  and  the  presence  or  absence  of  substances 
capable  of  affecting  the  equilibria  in  such  gas  systems.83  Thus  in  the 
coking  of  coal  the  gas  is  richest  in  methane  when  the  retort  tempera- 
ture is  within  the  range  600°  to  800°  but  as  the  retort  temperature  in- 
creases above  800°  the  per  cent  of  methane  in  the  evolved  gas  rapidly 
diminishes  and  the  per  cent  of  hydrogen  rapidly  increases.84  Gases 
containing  ethylene,  such  as  oil  gas  and  coal  gas,  are  invariably  not  in 
equilibrium  at  the  temperatures  at  which  they  are  produced  and  in 
practice  they  are  removed  and  cooled  before  equilibrium  at  the  higher 
temperature  is  established.  Ethylene  is  rapidly  decomposed,  above  600° 
to  methane  and  carbon  and  this  reaction  may  be  greatly  catalysed  by 
contact  with  iron  oxide  or  other  catalysts.  Fats  or  fatty  acids  readily 
break  down  on  heating  under  pressure  to  a  series  of  hydrocarbons, 
mainly  saturated,  which  closely  resemble  crude  petroleum  and  Eng- 
ler,85  has  used  this  fact  in  developing  his  theory  of  the  origin  of  pe- 
troleums. It  has  been  shown  that  in  the  heat  decomposition  of  heavy, 
high  boiling  mineral  oils  under  pressure,  the  lighter  oils  so  produced 

'"Slator.  J.  CJiem.  Foe.  109,  160   (1916). 

"Vignon,  J.  Gas  Lighting  121,  107;  Meyer,  Chem.  Abs.  8,  2795  (1914). 

85 Petroleum  7,  399    (1912). 


34        CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

consist  largely  of  hydrocarbons  of  the  paraffine  series,  which  may  be 
accounted  for  by  the  supposition  that  when  a  large  paraffine  molecule 
breaks  up  into  two  simpler  molecules,  one  will  be  a  saturated  paraffine 
and  the  other  an  olefine, 

R  CH2CH2  :  CH2  R  -       — >  R  CH3  +  CH2  =  CH.R  86 

• 

The  destructive  distillation  of  bituminous  shales,  lignites  and  peat 
yields  distillates  containing  paraffine  hydrocarbons;  and  paraffine  wax 
has  for  many  years  been  manufactured  from  the  distillates  of  shale 
in  Scotland.  By  the  distillation  of  ordinary  bituminous  coking  coal  at 
low  temperatures  a  distillate  rich  in  paraffine  wax  is  obtained.  These 
solid  paraffines  like  those  from  petroleum  are  normal  hydrocarbons  of 
24  to  29  carbon  atoms.87 

Effects  of  Heat  on  Non-Benzenoid  Hydrocarbons. 

The  changes  brought  about  by  heating  non-benzenoid  hydrocarbons 
have  long  been  of  industrial  interest  and  importance,  particularly  in 
'the  manufacture  of  oil  gas,  carburetted  water  gas,  the  pyrolysis  of  pe- 
troleum oils  for  the  manufacture  of  kerosene  and  more  recently  gaso- 
lene or  motor  fuel  from  heavier  hydrocarbons.  These  processes  are 
problems  of  technology  or  engineering,  rather  than  chemistry,  but  more 
recently  a  desire  to  know  more  concerning  the  chemical  reactions  in- 
volved and  their  relationships  has  been  indicated  by  the  character  of 
many  of  the  published  researches. 

The  two  fundamental  reactions  which  take  place  when  hydrocar- 
bons are  heated  to  the  decomposition  point  are,  first,  the  rupture  of 
the  carbon-to-carbon  structure  and  second,  the  dissociation  of  hydrogen 
from  carbon.  These  two  reactions  probably  occur  simultaneously  at- 
tended by  a  sequence  of  other  reactions,  but  special  catalysts  may 
greatly  accelerate  one  or  the  other  type  of  reaction,  for  example,  nickel, 
palladium  or  platinum  may  cause  dissociation  of  hydrogen  without 
alteration  of  the  carbon  structure,  as  in  the  conversion  of  cyclohexane 
to  benzene  in  the  presence  of  nickel  at  250°,  or  the  complete  rearrange- 
ment and  splitting  of  hydrocarbons  by  gentle  heating  in  the  presence 
of  anhydrous  aluminum  chloride,  in  which  case  methane  but  not  hy- 
drogen is  evolved. 

The  earlier  technical  investigations  of  the  pyrolysis  of  hydrocar- 

«  defines  of  this  type  are  unstable  and  rearrange,  cf.  pp.  (150,  151). 
"Glund,   Ber.  59,  1039    (1919). 


THE  PARAFFINES  35 

bons  centered  upon  coal  tar,  benzene,  naphthalene  and  their  deriva- 
tives. In  1866-7,  Berthelot  published  a  series  of  important  researches,88 
and  stated  that  at  a  "dull  red  heat"  equilibrium  was  established  be- 
tween ethylene,  hydrogen  and  ethane.  He  discovered  a  series  of  con- 
densations of  acetylene;  that  in  the  presence  of  coke,  acetylene,  at 
the  "temperature  at  which  glass  softens"  is  decomposed  almost  wholly 
to  hydrogen  and  carbon;  acetylene  and  ethylene  yield  a  condensation 
product  isomeric,  or  identical  with  crotonylene,  and  acetylene  and  ben- 
zene gave  naphthalene.  Benzene  passed  through  a  porcelain  tube  gave 
diphenyl,  chrysene  and  a  resinous  substance,  but  no  anthracene  or 
naphthalene.  Toluene  gave  benzene,  unchanged  toluene,  and  large  pro- 
portions of  naphthalene.  Xylene  gave  toluene  as  the  principal  product. 
Berthelot's  view  that  acetylene  was  the  parent  substance  of  the  ben- 
zenoid  hydrocarbons  was  vigorously  disputed  by  Thorpe  and  Young,89 
Armstrong  and  Miller  90  and  Haber  91  who  considered  that  hydrogen  or 
methane  were  first  formed,  the  residues  then  condensing  or  undergoing 
still  further  decomposition : 

2  G6H6 >  C12H10  (diphenyl)  +  H2 

C6H14  (hexane) »C5H10(amylene)  +  CH4 

They  pointed  out  that  usually  acetylene  cannot  be  detected  among 
the  products  of  pyrolysis.  Bone  and  Coward  92  have  made  a  careful 
study  of  the  thermal  decomposition  of  methane,  ethane,  ethylene  and 
acetylene  and  concluded  that  Berthelot's  theory  of  the  attainment  of 
equilibrium  between  dissociation  and  recombination  of  these  hydro- 
carbons is  not  borne  out  by  the  experimental  evidence.  Their  results 
show: 

(1)  Methane  is  exceedingly  stable.    It  decomposes  almost  exclusively 
into  hydrogen  and  carbon  and  this  decomposition,  though  rever- 
sible, is  mainly  a  surface  phenomenon,  at  least  at  moderate  tem- 
peratures. 

(2)  Acetylene  polymerizes  at  comparatively  low  temperatures,  the 
optimum  temperature  range  for  this  polymerization  being  600°- 
700°.    Acetylene  being  formed  from  ethylene,  condensation  prod- 
ucts of  acetylene  will  be  found  among  the  products  whenever 
ethylene  is  a  primary  product  of  the  pyrolysis  of  hydrocarbons. 

**Compt.  rend.  62,  905,  947  (1866)  ;  63,  788,  834  (1866)  ;  Bull.  Soc.  Chim,  (2)  7, 
217  (1867). 

MProc.   Roy.   Soc.  19,  370;   20,  488;   21,  184    (1873). 
™Chem.  News  49,  285;  Soc.  J,9,  74   (1886). 

91  J.  Gasbel,  39,  377,  395.  435,  452,  799;  Ber.  29,  2691    (1896). 
82  Soc.   93,    1197    (1908). 


36        CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

(3)  Ethylene  and  acetylene  combine  with  hydrogen  at  moderate  tem- 
peratures to  form  ethane.  Whitaker  and  Leslie  93  obtained  evi- 
dence of  hydrogenation  at  620°  when  hydrogen  was  introduced 
with  oil  in  an  experimental  apparatus  for  making  oil  gas.  These 
authors  also  call  attention  to  the  fact  that  in  decomposing  oil  to 
gaseous  products,  equilibrium,  or  rather  the  ultimate  composition 
which  a  given  temperature  tends  to  produce,  is  seldom  attained, 
even  in  apparatus  of  industrial  size,  owing  to  the  short  period 
of  time,  during  which  the  hydrocarbons  are  subjected  to  the  par- 
ticular temperature  of  the  operation.  One  reason  for  this  un- 
doubtedly lies  in  the  fact  that  some  of  the  reactions  taking  place 
in  such  systems  are  strongly  endothermic,  for  example, 

C2H6 >  C2H4  +  H2  =  31,270  calories 

and  such  reactions  can  be  maintained  only  by  the  absorption  of 
a  large  supply  of  energy.9* 

It  is  well  known  that  the  velocities  of  chemical  changes  are  greatly 
affected  by  relatively  small  changes  in  temperature.  It  is,  therefore, 
readily  understood  that  small  differences  of  operating  temperature  may 
cause  very  great  differences  in  the  character  of  the  pyrolytic  products, 
a  fact  apparently  first  appreciated  in  industrial  operations  by  Hall. 

Generally  speaking,  the  temperatures  employed  for  obtaining  mo- 
tor fuel  are  within  the  range  410°-500°  and  Rittman,  Button  &  Dean  95 
consider  that  the  maximum  yield  of  aromatic  hydrocarbons  (from  pe- 
troleum oils)  is  obtained  within  the  range  650°-700°.  Ipatiev  &6  states 
that  at  600°-700°  hexane  and  cyclohexane  yield  defines  and  other  hy- 
drocarbons, but  no  benzenoid  hydrocarbons.  Methyl  cyclopentane  was 
found  among  the  products.  Norton  and  Andrews  97  found  that  at  550° 
hexane  was  not  decomposed  and  was  very  slightly  affected  at  600° 
but  at  700°  decomposition  with  formation  of  gas,  methane  and  ethyl- 
ene,  propylene,  butylene,  amylene,  hexylene  and  butadiene  but  no 
benzene.  Iso-hexane  and  n .  pentane  show  approximately  the  same  sta- 
bility and  at  700°  yield  gas  and  a  series  of  defines.  Benzene  appears 
among  the  products  of  reaction  only  at  higher  temperatures.  Thus 
Haber  obtained  benzene  from  hexane  by  heating  to  800°  98  and  Wor- 
stall  and  Burwell  obtained  it  from  heptane  and  octane  at  900°." 

•»  J.  Ind.  &  Eng.  Chem.  8,  593,  684    (1916). 

MLomax,  Dunstan  &  Thole,  J.  Inst.  Petr.  Tectin.  3,  76    (1916). 

95  U.  S.  Bur.  Mines  Bull.  114,  Washington    (1916). 

MBcr.   It',,   1984,    2978    (1911). 

"Am.  Chem.  J.  8,  1   (1886). 

98Loc.  cit. 

99  Am.  Chem.  J.  19,  815   (1897). 


THE  PARAFFINES  37 

Benzene  and  its  simple  homologues  had  been  found  in  the  liquid 
ccndensate  obtained  by  compressing  oil  gas.100  Armstrong  and  Miller 
made  a  careful  study  of  this  liquid  condensate  from  oil  gas  and  iden- 
tified propylene,  amylene,  hexylene,  heptylene,  crotonylene,  isoal- 
lylethylene,  benzene,  toluene,  xylenes,  mesitylene,  pseudo-cumene  and 
naphthalene.  In  1878,  a  number  of  processes  were  described  101  which 
sought  to  manufacture  benzene  hydrocarbons  from  Russian  petroleum 
by  passing  the  oil  through  red-hot  tubes  packed  with  various  materials 
(the  function  of  which  was  not  evident) .  None  of  these  processes  were 
industrially  successful.  Nikiforoffs'  process  was  apparently  a  develop- 
ment from  the  well  known  Pintsch  gas  process,  the  oil  being  first  de- 
composed or  vaporized  at  525°-550°  and  then  passed  through  retorts, 
similar  to  the  older  type  of  Pintsch  gas  retort,  at  700°-1200°  under  a 
pressure  of  about  two  atmospheres.  No  further  important  work  on 
the  manufacture  of  benzene  hydrocarbons  from  petroleum  oils  by  the 
action  of  heat,  in  the  absence  of  catalysts,  was  made  until  the  recent 
war  period  when  Hall,  working  in  England,  and  Rittman  and  his  co- 
workers  in  the  United  States,  developed  processes,  which  were  operated 
industrially.  Hall  decomposes  oil  at  550°-600°  and  under  a  pressure 
of  about  70  pounds  per  square  inch  when  motor  fuel  is  the  desired  prod- 
uct and  for  benzene  and  toluene  the  operating  temperature  is  750°  and 
the  pressures  100  to  110  pounds  per  square  inch.102  A  noteworthy  me- 
chanical feature  of  the  Hall  process  is  very  rapid  passage  of  the  oil 
and  vapors  through  the  heated  tubes,  which  minimizes  the  deposition 
of  carbon.  Rittman  employed  a  temperature  of  700°  and  a  pressure  of 
150  pounds  per  square  inch.  In  connection  with  this  work,  which 
probably  should  be  regarded  as  a  war  time  industry,  at  least  so  far  as 
the  manufacture  of  benzene  and  toluene  from  petroleum  is  concerned, 
much  valuable  experimental  work  was  done.  Commercial  gas  oil, 
specific  gravity  0.817  at  15.5°  and  boiling  at  200°-350°,  in  the  Rittman 
apparatus  gave  a  maximum  yield  of  toluene,  3.1  per  cent  by  volume, 
at  650°.  The  maximum  yield  of  benzene,  4.4  per  cent  by  volume  was 
obtained  at  800°.  The  maximum  yield  of  xylene  was  1.9  per  cent  at 
750°. 103 

Other  conditions  being  equal,  higher  yields  of  aromatic  hydro- 
carbons are  obtained  from  petroleum  containing  relatively  large  pro- 

i<x>  Armstrong  and  Miller,  J.  Chem.  Soc.  49,  74  (1886)  ;  Williams,  Chem.  News  49, 
197  (1884). 

101Letny,  Bcr.  11,  1210  (1878)  ;  Liebermann  &  Burg,  Ber.  11,  723  (1878)  ;  Salzmann 
&  Wichelhaus,  Ber.  11,  1431  (1878). 

592  TT.  S.  Pat.  1.175.909;  Brit.  Pat.  24,491  (1913);  437  (1914);  2948  (1914); 
7282  (1914);  12,962  (1914);  1594  (1915);  U.  S.  Pat.  1,194,289;  1,175,910. 

103Egloff,  Met.  &  Chem    Eng.  16,  492   (1917). 


38        CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


portions  of  benzene  and  naphthalene  derivatives  and  cyclohexane  de- 
rivatives, such  as  Borneo  petroleum.  The  oil  from  the  deeper  strata 
of  the  Kotei  field  in  Borneo  was  used  in  England  during  the  war  for 
the  manufacture  of  benzene  and  toluene.  Jones  and  Wooton  first 
called  attention  to  the  unusual  character  of  this  oil  and  more  recently 
Chavanne  and  Simon  104  have  examined  the  gasoline  fraction  of  this 
oil  and  state  that  they  have  identified  cyclopentane,  methylcyclopen- 
tane,  cyclohexane,  a  dimethylcyclopentane,  methylcyclohexane  and 
dimethylcyclohexane.  During  the  war  gasoline  from  this  petroleum 
was  sent  to  England  where  benzene  and  toluene  were  made  from  it  in 
a  fair  degree  of  purity.  This  gasoline  contained  about  40  per  cent  of 
aromatic  hydrocarbons  of  which  about  7  per  cent  was  benzene,  14  per 
cent  toluene,  15  per  cent  xylenes  and  4  per  'cent  higher  homologues.105 
Brooks  and  Humphrey  106  found  small  quantities  of  benzene  and  tolu- 
ene in  gasoline  made  by  distilling  heavy  Oklahoma  oil  at  the  relatively 
low  temperature  of  420°  and  a  pressure  of  100  pounds  per  square  inch. 
Small  yields  of  aromatic  hydrocarbons  were  also  obtained  from  heavy 
high-boiling  petroleums  by  heating  with  anhydrous  aluminum  chloride 
and  since  the  temperature  employed  in  the  first  method  is  considerably 
below  that  at  which  benzene  has  been  observed  to  be  formed  from 
paraffines  or  na'phthenes,  they  conclude  that  high  boiling  benzene  de- 
rivatives are  present  in  the  original  oil,  benzene  being  obtained  by  their 
splitting  or  "cracking." 

It  was  apparent  from  much  of  the  early  work  on  pyrolysis  that  the 
character  of  the  products  obtained  was  not  solely  a  function  of  the  tem- 
perature employed  but  also  of  the  time  or  duration  of  the  heating  and 
also  the  presence  or  absence  of  various  substances  acting  catalytically 
upon  the  decomposition,  either  hydrogen  dissociation  or  splitting  of 
the  carbon  structure,  or  affecting  one  or  more  of  the  secondary  re- 
actions, for  example  polymerization  of  the  olefines  which  are  formed. 
Before  discussing  the  effect  of  catlysts  the  results  of  pyrolysis  at  mod- 
erate temperatures  will  be  noted. 

One  of  the  most  conspicuous  differences  in  the  results  of  low  tem- 
perature decomposition  is  the  greatly  decreased  yield  of  gas.  Exact 
comparisons  are  difficult  to  make  on  account  of  variable  time  factors, 
different  distribution  and  character  of  the  heated  surfaces  and  the  like. 
Hall  states  that  in  the  industrial  tube  type  of  apparatus  developed  by 
him  a  change  of  operating  temperature  from  540°  to  580°  results  in  an 

104  Compt.  rend.  1919,  285. 
106Kewley,   Chem.   Tr.  J.  1921,  380. 
109  J.  Am.  Chem.  Soc.  88,  393    (1916). 


THE  PARAFFINES  39 

increase  of  50  per  cent  in  the  quantity  of  gas  obtained.  In  a  small  ex- 
perimental pressure  still  Brooks,  Padgett  and  Humphrey 107  found, 
when  distilling  85  per  cent  of  the  oil  used  [heavy  Oklahoma  gas  oil] , 
under  pressure,  that  at  50  pounds  pressure  and  a  mean  temperature  of 
410°,  24.8  liters  of  gas  were  formed  per  liter  of  distillate;  at  150 
pounds  pressure  and  a  mean  temperature  of  425°,  58  liters  of  gas  per 
liter  of  distillate  were  produced.  The  relative  area  of  heated  surface 
(iron)  in  this  small  apparatus  was  quite  large,  as  compared  with  oil 
distilling  apparatus  of  industrial  dimensions  of  the  Burton  type,  but 
the  results  are  indicative  of  the  large  difference  in  gas  yield  resulting 
from  a  comparatively  slight  temperature  change.  The  effect  of  in- 
creased pressure  should,  per  se,  decrease  the  gas  yield  by  polymerizing 
the  olefines.  That  higher  temperatures  give  large  proportions  of  ole- 
fines  in  the^gas  is  indicated  by  the  following  table: 

COMPOSITION  OF  OIL  GAS  MADE  IN  TUBES  MAINTAINED  AT  DEFINITE 
TEM  PERAT  URES  ,108 

Temperature,  deg.  C  600.  650.  700.  730. 

Pressure,  Ib 57.  72.  83.  95. 

Ethylene,  per  cent   19.3  19.0  17.7  17.5 

Propylene,  per  cent  28.0  28.4  23.9  20.0 

Higher  olefines,  per  cent 3.2  4.2  3.5  3.1 

Total  olefines,  per  cent 50.5  51.6  45.1  40.6 

GASES  FROM  CRACKING  DISTILLATIONS  UNDER  lOO-Ls.  PRESSURE. 
From  Jennings  Crude 

1  2  3 

340°  415°  422° 

Temperature  in  still                                                      Per  Cent  Per  Cent  Per  Cent 

CO2 12  0.5  0.0 

CO   1.2  0.5  1.3 

Illuminants    15.4  15.3  13.0 

Hydrogen    0.0  4.0  4.4 

Saturated  Hydrocarbons  81.5  79.7  81.3 

From  Paraffine 

417°  432°  437° 

Temperature  in  still                                                         Per  Cent  Per  Cent  Per  Cent 

CO2   0.0  0.0  0.0 

CO   0.0  0.0  0.0 

Illuminants    25.4  37.0  33.5 

Hydrogen    0.3  0.9  3.0 

Saturated  Hydrocarbons  74.3  62.1  63.5 

Analyses  of  oil  gas  are  usually  reported  in  terms  of  total  olefines, 
or  illuminants,  hydrogen  and  methane.  Accurate  analyses,  with  respect 
to  methane,  ethane,  propane  and  other  hydrocarbons,  made  by  the 
method  of  fractional  distillation  at  low  temperatures  have  not  been  re- 

107  J.  Frankl.  Itist.  180,  653    (1915). 

108  Hall  type  of  apparatus,   industrial  size. 


40 


CHEMISTRY  OF  THE  NON-BENZEN01D  HYDROCARBONS 


ported.  The  relative  proportions  of  ethylene,  propylene  and  other 
defines  in  oil  gas  made  at  different  temperatures  in  a  commercial  size 
Pintsch  gas  apparatus  is  given  in  the  following  table: 

PER  CENT  ETHYLENE  AND  PROPYLENE  IN  OIL  GAS. 


Higher 

Temp.                                                            Olefines  Per 

Deg.  C                                                          Per  Cent  Cent 

805-650  ...............................     1.4  18.6 

660-535  ..............................  1.6  19.0 

635-535  ...............................  2.4  22.4 

625-535  ...............................  2.6  22.6 

615-425  ...............................  3.8  25.7 


C2H4 
Per 
Cent 
16.3 
18.3 
12.5 
13.7 
12.0 


Total 
Olefmes 
Per  Cent 

36.3 

38.9 

37.3 

38.5 

41.5 


The  composition  with  respect  to  olefines  of  gas  made  at  definite 
temperatures  in  a  large  industrial  size  apparatus  of  the  Hall  type  is 
as  follows:  109 

PER  CENT  OIL  GASIFIED  IN  HALL  TYPE  APPARATUS  AT  DIFFERENT  TEMPERATURES. 

Per  Cent 
Temperature  Per  Cent       Ethylene  and 


Deg.  C 
605 
625 
645 
665 


Gas 
17.7 
26.6 
37.6 
40.0 


685    , 40.8(?) 

705 48.7 

725    .    66.6 


Propylene 
47.9 
46.1 
44.9 
43.7 
42.6 
39.5 
38.5 


Typical  analyses  of  commercial  gases  are  of  interest  particularly 
as  regards  the  relative  proportions  of  methane,  ethane,  hydrogen  and 
illuminants.110 

AVERAGE  COMPOSITION  OF  COMMERCIAL  GASES. 


Coal  gas 

Carburetted  water  gas 

Pintsch  gas    

Blau  gas   

All  oil  water  gas 7.0 

Oil  gas   31.3 

Blue  water  gas   

Producer  gas   (coal) . . . 
Producer  gas  (coke) . . . 

•Blast  furnace  gas  

Wood  gas   (pine) 10.6 

v v '  (   ^00 

Oil  gas,  Dayton  process"1    14.7      5.6      1.7          7.8         6.1    ..     63.2     ...   |  390 

"•Brooks,  Chem.  &  Met.  Eng.  2%,  April  7,  1920. 

110  Rogers'  Industrial  Chemistry  Ed.  2.     Fulweiler,  p.  474. 

111  Binnall,   Gas  Age  47,  47    (1921).     This  process  depends  upon   the  partial  com- 
bustion  of  the  oil  sufficient  to   raise   sufficient   heat   to   gasify   the   remainder.     About 
4  gallons  of  oil   are   required  to  make   1000   cubic  feet  of  gas  of  450   B.   T.   U.     The 
per  cent  of  nitrogen  is  naturally  high. 


Ilium.  CO 

H2 

CH4 

C2H6C02   O2 

N2 

Cdl. 

%•     %       %%%%%%      Pr.  B.T.U. 

4.0 

8.5 

49.8 

29.5 

3.2 

1.6 

.4 

3.2 

16.1 

622 

13.3 

30.4 

37.7 

10.0 

3.2 

3.0 

.4 

2.1 

22.1 

643 

30.0 

.1 

13.2 

45.0 

9.0 

.2 

.0 

1.6 

43.0 

1276 

51.9 

.1 

2.7 

44.1 

.0 

.0 

.0 

1.2 

48.2 

1704 

7.0 

9.2 

39.8 

34.6 

2.6 

.2 

6.6 

19.7 

680 

31.3 

2.4 

13.5 

46.5 

3.0 

.3 

.0 

1.1 

38.0 

1320 

.0 

40.9 

50.8 

.2 

.0 

3.4 

.9 

3.5 

299 

.2 

17.6 

10.4 

6.3 

.0 

7.3 

.7 

58.1 

... 

161 

.0 

25.3 

13.2 

.4 

.0 

5.4 

.6 

55.2 

137 

.0 

26.5 

3.5 

.2 

12.8 

.1 

56.9 

100 

10.6 

27.1 

32.7 

21.5 

4.9 

.4 

2.6 

607 

THE  PARAFFINES 


41 


Although  data  obtained  in  making  oil  gas  on  a  small  experimental 
scale  have  no  close  industrial  parallel,  the  experimental  results  of 
Whitaker  and  Rittman  112  are  of  interest  as  indicating  the  very  marked 
effect  of  variations  of  temperature  and  pressure. 

OIL  GAS  EXPERIMENTS  OF  WHITAKER  &  RITTMAN.* 
Pressure 


Temp. 

Ib.  per 

Gas 

Carbon 

Tar 

CH* 

CA 

H2 

Ilium. 

°C 

sq.  in. 

Liters 

Grams 

c.c. 

Liters 

Liters 

Liters 

Liters 

650° 

15. 

135 

3 

163 

45.5 

13.8 

12.1 

58.8 

650° 

45. 

145 

8 

133 

65.2 

16.7 

13.1 

44.3 

750° 

0.75 

146 

1 

153 

.... 

18.3 

82.0 

750° 

15. 

206 

18 

80 

84.5 

Vo.is 

39.6 

63.0 

750° 

45. 

194 

26 

87 

110.0 

11.8 

33.9 

30.1 

900° 

0.75 

235 

12 

58 

63.4 

trace 

48.8 

110.0 

900° 

15.0 

382 

115 

11 

178.1 

trace 

148.2 

50.0 

900° 

45.0 

310 

165 

9 

128.9 

none 

155.0     A 

15.5 

*40<*  Oil  used. 


In  a  later  paper  Whitaker  and  Alexander  113  showed  that  under  the 
same  experimental  conditions  the  composition  of  the  gas  produced 
varies  with  the  rate  of  oil  feed,  within  rather  wide  limits,  and  that  even 
at  comparatively  slow  rates  of  oil  feed  equilibrium  is  not  reached. 
Thus  it  has  been  shown  that  at  1200°  hydrogen  is  in  equilibrium  with 
carbon  and  about  0.3  per  cent  methane,  but  Whitaker  and  Alexander 
find  6  to  10  per  cent  methane  in  their  most  slowly  conducted  experi- 
ments 114  and  they  emphasize  the  fact  that  equilibrium  compositions 
are  not  obtained  in  gas  making  practice  and  that  it  would  be  im- 
practical to  run  an  oil  gas  generator  at  such  rates  of  oil  feed  as  would 
even  approximate  equilibrium  conditions. 

Zanetti 115  obtained  typical  oil  gas  by  decomposing  the  propane 
fraction  of  natural  gas  gasoline  at  750°,  obtaining  ethylene,  propylene, 
butylene  and  small  quantities  of  liquid  hydrocarbons  and  tars. 

In  view  of  the  fact  that  the  coking  of  coal  at  low  temperatures 
yields  a  distillate  containing  paraffine  wax,  naphthenes  and  olefines 
and  resembling  crude  shale  oil  in  its  general  character  the  coking  of 
coal  at  higher  temperatures  with  the  formation  of  coal  gas  and  typical 
coal  tars  should  be  regarded  as  essentially  paralleling  the  high  tem- 
perature pyrolysis  of  mineral  oils,  in  contact  with  coke  or  carbon. 

112  J.  Ind.  d  Eng.   Chem.  6,  479    (1914). 

113  J.  Ind.  &  Eng.  Chem.  7,  484  (1915). 

14  The  commercial  manufacture  of  hydrogen  by  heating  methane  or  other  hydro- 
carbons to  1200°-1300°  has  been  proposed,  with  various  modifications,  for  example  see 
Uhlinger,  U.  S.  Pat.  1,363,488. 

116  J.  Ind.  &  Eng.  Chem.  8,  674   (1916). 


42        CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

As  regards  the  liquid  products  of  pyrolysis  of  high  boiling  hydro- 
carbons at  moderate  temperatures,  low  temperature,  pressure  and  slow 
operation  favor  the  formation  of  saturated  low  boiling  hydrocarbons. 
Hall  and  others  have  called  attention  to  the  relatively  large  yields  of 
defines  and  diolefines  obtained  at  550°-600°.  Such  distillates  are  said 
to  be  "highly  cracked,"  absorb  oxygen  readily,  a  very  general  property 
of  diolefines  (see  pages  212,  216)  forming  a  resinous  oxidation  product 
which  is  often  noticed  as  a  sticky  film  when  such  oil  is  permitted  to 
evaporate.  Such  distillates,  containing  diolefines,  react  energetically 
with  sulphuric  acid  forming  tars.  Slow  distillation  under  pressure 
evidently  polymerizes  the  defines  since  hydrogenation  of  hydrocarbons 
at  400°-450°  in  the  absence  of  catalysts  and  under  moderate  pressures 
has  not  been  observed.  Although  Bergius  has  hydrogenated  fatty  oils 
in  the  ar>sence  of  finely  divided  metallic  catalysts  by  heating  with  hy- 
drogen under  30  atmospheres,116  no  hydrogenation  of  unsaturated  pe- 
troleum hydrocarbons  could  be  detected  by  Brooks  117  on  heating  at 
196°  for  30  hours  under  a  hydrogen  pressure  of  3000  pounds  per  square 
inch.  However,  Ipatiev  118  noted  evidence  of  hydrogenation  at  higher 
temperatures  and  under  pressures  up  to  340  atmospheres. 

The  low  boiling  hydrocarbons  produced  at  moderate  temperatures 
are  mainly  normal  saturated  paraffines  as  has  been  shown  by  Hum- 
phrey in  the  case  of  a  distillate  made  from  the  heavy  residues  of 
Oklahoma  petroleum  by  distilling  at  400°-420°  and  100  pounds  pres- 
sure.119 The  presence  of  small  quantities  of  benzene  and  its  homo- 
logues  in  such  distillates  has  been  noted. 

Among  the  diolefines,  which  have  been  identified  in  the  low  boiling 
fractions  butadiene  and  isoprene  have  been  repeatedly  noted.  The 
yield  or  relative  proportions  of  these  hydrocarbons  obtainable  in  this 
way  is  quite  small.  Engler  and  Staudinger,120  however,  have  patented 
the  manufacture  of  these  conjugated  diolefines  by  the  thermal  decom- 
position of  mineral  oils.  Pyrolysis  under  reduced  pressure  increases  the 
proportion  of  unsaturated  hydrocarbons,  at  least  among  the  gaseous 
products.121 

The  polymerization  of  defines  by  heating  under  pressure  has  been 
frequently  observed.  Ethylene,  the  most  stable  known  olefme,  is 
polymerized  in  the  presence  of  iron  at  380°-400°  and  70  atmospheres 

16  Z.  angew.  Chem.  191^,  522. 

7  J.  Frank.  Inst.  1915,  658. 

8  Ber.  37,  2961    (1904). 

°J.  Ind.  d  Eng.  Chem,  7,  180   (1915). 
20  German  Pat.  265,172    (1912). 
121  Whitaker   &   Rittman   loc.   cit. 


THE  PARAFFINES  43 

pressure,  a  complex  mixture  of  hydrocarbons  being  formed.122  The 
polymerization  of  conjugated  diolefines  at  moderate  temperature  and 
pressures  has  been  applied  to  the  synthesis  of  rubber  (see  page  000) 
and  Semmler 123  has  condensed  isoprene  with  limonene  and  other  ter- 
penes  at  275°  to  form  new  sesquiterpenes  of  the  empirical  formula 
C15H24.  Lebedev124  has  polymerized  allene  by  heating  in  glass  at 
140°  obtaining  5%  dimeride,  15%  trimeride  and  80%  of  more  highly 
polymerized  material.  Diallyl  is  very  slowly  polymerized  at  250°  to 
a  dimeride  and  a  gummy  residue.  At  150°  2  :  4  hexadine  yields  chiefly 
the  dimeride.  The  polymerization  of  defines  is  markedly  catalyzed 
by  many  substances.  Gurwitsch  125  polymerized  amylene  by  fuller's 
earth  at  ordinary  temperature  and  Hall  polymerized  the  resin-forming 
constituents  (diolefines)  contained  in  light  pyrolytic  gasoline  distillate, 
by  passing  the  hot  vapors  through  a  column  of  fuller's  earth.  Fuller's 
earth,  kaolin  and  alumina  are  said  to  slightly  increase  the  yield  of  low- 
boiling  hydrocarbons. 

The  effect  of  nickel  in  a  finely  divided  condition  in  bringing  about 
equilibrium  conditions  between  unsaturated  hydrocarbons,  hydrogen 
and  saturated  hydrocarbons,  has  led  to  quite  changed  conceptions  re- 
garding the  stability  of  hydrocarbons.  The  earlier  work  had  to  do 
almost  exclusively  with  the  formation  of  saturated  hydrocarbons,  with 
yields  which  were  practically  quantitative.  The  reversible  nature  of 
the  reaction  was  not  clearly  recognized  until  Sabatier  and  Senderens 
showed  that  cyclohexane  was  converted  into  benzene  in  the  presence 
of  finely  divided  nickel  at  270°-280°.  Zelinsky  126  showed  that  cyclo- 
hexane and  methylcyclohexane  are  reduced  to  benzene  and  toluene 
respectively,  together  with  free  hydrogen,  by  heating  in  the  presence  of 
finely  divided  palladium.  The  reaction  is  appreciable  at  about  190°, 
and  within  the  range  200°-300°,  the  equilibrium  mixture  contains  very 
large  proportions  of  benzene.127  No  dihydro  or  tetrahydro  derivatives 
were  found  among  the  reaction  products.  Hexane,  cyclopentane  and 
methylcyclopentane  are  more  stable,  and  do  not  yield  free  hydrogen 
appreciably  below  300°.  The  extraordinary  stability  of  methylcyclo- 
pentane as  compared  with  cyclohexane  is  shown  by  later  experiments 
of  Zelinsky,  in  which  a  mixture  of  methylcyclopentane  and  cyclohexane 

«*Ipatiev,  J.  Rusa.  S8,  I,  63  (1906). 

113  Ber.  47,  2068,  2252    (1914). 

mJ.   S.  C.  I.  1914,  1224. 

118  J.  Rus8.  47,  827    (1915). 

1MJ.  Rusa.  Phy*.-Cli€m.  Soc.  J,S,  1220  (1911)  ;  Ber.  44,  3121  (1911). 

127  Tausz  &  Putnoky,  Ber.  52,  1573  (1919),  state  that  in  the  presence  of  palladium 
black  the  formation  of  benzene  from  cyclohexane  is  practically  quantitative  at  270°- 
300°.  They  confirm  the  absence  of  cyclohexane  in  Pennsylvania  gasoline  by  testing 
for  the  formation  of  benzene  under  these  conditions. 


44        CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

were  passed  over  palladium  black  at  300°,  until  no  further  hydrogen 
was  evolved.  The  cyclohexane  was  converted  to  benzene,  thus  offer- 
ing a  convenient  and  easy  method  of  separating  these  two  hydrocar- 
bons.128 

That  these  results  are  brought  about  by  the  catalysts  is  indicated 
by  many  observations,  for  example,  Ipatiev  129  had  shown  previously, 
that  benzene  is  not  formed  from  cyclohexane  or  hexane  on  passing  the 
vapors  through  an  iron  tube  heated  to  650°-700°  C.  At  considerably 
lower  temperatures,  cyclohexane  is  readily  formed  from  benzene,  the 
reaction  being  very  rapid  in  the  presence  of  finely  divided  nickel  and 
hydrogen  at  160°.  The  catalytic  effect  of  iron,  copper  and  aluminum 
on  the  dissociation  or  addition  of  hydrogen  is  very  slight.  Whether 
or  not  the  iron  surface  of  pressure  stills  and  similar  apparatus  have 
any  catalytic  effect  on  the  pyrolytic  changes  effected  by  heating  pe- 
troleum oils  is  not  certain,  but  since  very  finely  divided  iron  has  only 
a  very  slight  effect,  the  catalytic  effect  of  the  iron  or  steel  surfaces  of 
industrial  apparatus  is  probably  negligible. 

It  has  frequently  been  proposed  to  insert  catalysts  into  pressure 
stills  and  similar  apparatus  with  the  object  of  hydrogenating  the  de- 
fines which  distillates  made  in  this  way  normally  contain,  but  these 
methods  have  had  no  technical  success.  Nickel,  the  most  active  cat- 
alyst of  this  type,  is  very  quickly  covered  with  coke  and  thereby  ren- 
dered inactive.130  Sabatier  and  Mailhe  proposed  to  remove  the  carbon 
from  the  metal  catalyst  by  heating  in  a  current  of  steam.131 

The  lower  temperatures  at  which  the  reaction  of  steam  and  carbon 
becomes  appreciable  have  not  been  determined  and  this  doubtless  varies 
considerably  with  different  forms  of  carbon.  Bergius  has  converted 
carbon  and  water  to  hydrogen  and  C02  by  heating  at  300°  and  150 
atmospheres  pressure  for  20  days.  Although  water  gas  has  been  manu- 
factured for  many  years,  high  temperatures  are  always  employed  since 
it  has  long  been  known  that  low  temperatures  favor  the  formation  of 
CO2  in  the  gas  equilibrium  CO  +  H20  ±+  C02  +  H2.132  A  number  of 
patents  have  described  the  decomposition  of  heavy  oils  in  the  presence 
of  steam  and  one  patentee  claims  that  iron  acts  as  a  catalyst  in  this 
steam-hydrocarbon  mixture.133  This  process  has  been  carried  out  on  a 

ls*Ber.  45,  678    (1912). 

128  Ber.  44,  2987    (1911). 

130  The  manufacture  of  hydrogen  from  methane  in  the  presence  of  nickel  at  700° 
as  proposed  in  the  Badische  process,  French  Pat.  463,114  (1913),  is  undoubtedly  sub- 
ject to  this  difficulty. 

l«U.  S.  Pat.  1,152,765    (1915);  TJ.   S.  Pat.  1,124,333   (1915). 

182  Taylor  &  Rideal :  Catalysis,  p.  158. 

"»Noad  &  Townsend,  Brit.  Pat.  113,675   (1908). 


THE  PARAFFINES  45 

fairly  large  scale,  the  tubes  or  retorts  being  packed  with  .iron  turnings 
and  a  temperature  of  about  600°  maintained.  Greenstreet  claims  that 
the  presence  of  steam  in  the  zone  of  decomposition  prevents  the  depo- 
sition of  carbon  or  reacts  with  the  carbon  to  form  carbon  monoxide  and 
hydrogen,  the  hydrogen  being  supposed  to  be  taken  up  by  the  un- 
saturated  hydrocarbons.  In  the  presence  of  nickel,  Sabatier  observed 
the  reaction  of  steam  and  carbon  to  C02  and  hydrogen  at  500°. 

The  only  catalytic  process  which  has  shown  great  industrial  prom- 
ise is  of  an  altogether  different  type  from  the  catalysts  discussed  in  the 
foregoing  paragraphs.  Abel  and  also  Friedel  and  Crafts  described  the 
decomposition  of  petroleum  hydrocarbons  by  heating  with  anhydrous 
aluminum  chloride.134  Gustavson  noted  a  similar  behavior  with  alu- 
minum bromide.  Heusler  noted  that  unsaturated  hydrocarbons  are 
polymerized  by  aluminum  chloride  and  also  that  sulfur  derivatives 
are  decomposed  and  the  sulfur  removed.135  Aschan  also  noted  the 
polymerization  of  olefines  in  the  presence  of  this  reagent  and  Engler 
observed  that  amylene,  heated  with  anhydrous  aluminum  chloride,136 
yielded  a  mixture  of  polymers  resembling  natural  lubricating  oil. 

A  number  of  patents  have  been  recently  issued  to  McAfee,137  who 
has  determined  the  technical  refinements  necessary  in  the  utilization 
of  this  catalyst.  In  addition  to  a  little  gas  and  a  mixture  of  volatile 
saturated  hydrocarbons  including  an  excellent  grade  of  gasoline,  a 
heavy  viscous  residue  is  formed,  which  contains  the  greater  part  of  the 
aluminum  chloride.  This  material  is  very  readily  carbonized  when 
heated,  and  the  recovery  of  aluminum  chloride  from  these  residues  is 
the  really  difficult  part  of  the  problem,  at  least  from  a  technical  and 
economical  standpoint.  The  effect  of  anhydrous  zinc  chloride  and 
anhydrous  ferric  chloride  is  similar  but  much  less  effective. 

Synthesis  of  the  Paraffines. 

The  reduction  of  alky!  halides  (chlorides,  bromides  or  iodides)  by 
nascent  hydrogen  has  been  accomplished  in  a  number  of  ways.  The 
method  of  Gladstone  and  Tribe  138  of  reducing  alkyl  iodides  in  alcohol 
solution  by  'the  copper-zinc  couple  has  been  most  fruitful.  Many  of 
these  e'arlier  methods  were  discovered  in  the  attempt  to  isolate  the  so- 
called  radicals;  for  example,  Frankland  showed  that  heating  the  sim- 
pler alkyl  iodides  with  water  and  zinc  gave  the  corresponding  hydro- 

"*  Friedel  &  Crafts,   Compt.   rend.   100,  692;   Gustavson,   J.   prakt.   cJiem.   31,  161; 
Egloff  &  Moore,  Met.  &  Chem.  Eng.  15,  67,  340  (1916). 
135  Brit.   Pat.   4769    (1877). 

138  Z.  angew.  Chem.  9,  288,  318   (1893)  ;  Ber.  J,2,  4613  (1909). 
137  U.   S.  Patent.  1,099,096;   1,127,465  and  1,144,304. 
188  Ber.  6,  202,  454,  1136,  1873;  J,   Chem.  Soc.  45,  154   (1884). 


46        CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

carbons,  possibly  through  the  intermediate  formation  of  zinc  dialkyls. 
When  pure  zinc  dialkyls  are  treated  with  water  very  energetic  decom- 
position occurs  with  the  formation  of  a  hydrocarbon  and  zinc  hydrox- 
ide. 

Zn(C2H5)2  +  2H20 »  Zn(OH)2  +  2C2H6 

This  method  has  been  displaced  by  the  well-known  Grignard  reaction, 
the  simpler  alkyl  halides  readily  yielding  alkyl  magnesium  halides 
which  are  quantitatively  decomposed  by  water  to  give  hydrocarbons. 

C2H5Br  +  Mg  +  (C2H5)20 »  C2H5MgBr.  (C2H5)20 

OH 

C2H5MgBr .  (C2H5) 20  +  H20  ->  Mg  +  C2H6  +  (C2H5) 20 


\, 


Ammonia  or  an  amine  may  be  employed  instead  of  water  to  decompose 
the  magnesium  complex.  It  should  be  pointed  out,  however,  that  an- 
other reaction  takes  place  with  magnesium  and  alkyl  halides  which, 
though  a  very  subordinate  reaction  in  the  case  of  the  simpler  alkyls,  be- 
comes the  principal  result  with  halogen  derivatives  containing  six  or 
more  carbon  atoms.139  Thus,  like  the  condensation  of  propyl  bromide 
by  metallic  sodium  to  form  n.hexane,  propyl  bromide  and  magnesium, 
in  ether,  yields  a  small  amount  of  n.hexane  as  expressed  by  the  re- 
action, 

C3H7Br+Mg >C3H7MgBr 

C3H7MgBr  +  C3H7Br >  MgBr2  -f  C6H14 

This  reaction  is  an  admirable  method  of  synthesis  within  certain 
limits.140  Thus  in  the  terpene  series  halides  such  as  bornyl  chloride 
react  so  slowly  with  magnesium  that  the  Grignard  reactions  are  of 
practically  no  value  for  halogen  derivatives  of  this  class.  Hydrocar- 
bons of  an  odd  number  of  carbon  atoms  may  be  synthesized  by  a  slight 
modification  of  the  method,  for  example, 

C3H7MgBr  +  C4H9  Br >  MgBr2  +  C7H16 

C4H9MgBr  +  C.H^Br >  MgBr2  +  C0H20 

A  modification  of  the  above  method  has  proven  most  satisfactory  for 
the  preparation  of  tetramethyl  methane,  the  magnesium  complex 
(CH3)3C.MgI  being  treated  with  methyl  sulfate.141 

189  Grignard  &  Tissier,  Compt.  rend.  132,  835   (1901). 

140  Alkyl  groups  may  be  introduced  in  the  benzene  ring  by  treating  magnesium 
phenyl  bromide  with  propyl  or  allyl  bromide.  Tiffeneau,  Compt.  rend.  1^5,  437  (1907)  ; 
Kling,  Compt.  rend.  1-37,  756  (1903)  ;  Brit.  Pat.  122,  630  (1919). 

i«Ferrario  &  Fogetti,  GO&Z.  CMm.  Ital.  38,  II,  630   (1908). 


THE  PARAFFINES  47 

The  Grignard  reaction  has  a  wide  range  of  usefulness  in  building 
up  substances  having  the  carbon  atom  structures  of  the  hydrocarbons 
desired,  the  hydrocarbons  themselves  then  being  obtained  by  other 
methods,  for  example, 

C2H5 

RCHO  +  C2H5MgX-     ~>RCH 

OH 


RCOCH3  +  C2H5MgX 


RCOOCH3  +  2C2H5MgX 


CH2 
RMgX+  ]__  >0 >RCH2CH2OH 


CH, 


the  alcohols  thus  obtained  being  converted  to  hydrocarbons  by  means 
of  the  corresponding  iodide  and  reduction,  or  by  decomposing  the  alco- 
hols or  corresponding  halides  to  olefines  and  hydrogenating  the  latter. 
Hydriodic  acid  has  been  widely  employed  for  the  purpose  of  ener- 
getic reduction.  Berthelot 142  heated  alcohols  or  alkyl  halides  with 
concentrated  hydriodic  acid  in  sealed  tubes  and  discovered  that  reduc- 
tion occurs  as  follows, 

C2H5I  +  HI-     _*C2H6  +  I2 

Fatty  acids  may  be  reduced  to  paraffines  of  the  same  number  of  carbon 
atoms  by  this  method  and  Krafft 143  prepared  the  normal  paraffines 
from  nonane  to  tetracosane,  C24H50,  by  converting  the  ketones,  made 
through  the  lime  salts  of  the  fatty  acids,  into  the  corresponding  chlo- 
rides and  reducing  the  latter  with  hydriodic  acid  (in  the  presence  of 
red  phosphorus). 

(C10H21)2CO >  (C10H21)2CC12 >  (C10H21)2CH2  or  C21H44 

14*J.  prakt.  ctiem.    (1),  101,,  103   (1868). 
iaBer.  15,  1687,  1711   (1882)  ;  IS,  2218   (1886). 


48        CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

Magnesium  amalgam  has  been  employed  for  the  reduction  of  alkyl 
halides  by  Meunier  144  and  Wislicenus  showed  that  the  aluminum-mer- 
cury couple  is  of  wide  applicability.145  Thus  isobutyl,  n. butyl  and 
n.propyl  iodides,  treated  with  the  aluminum-mercury  couple,  give  the 
corresponding  hydrocarbons  in  nearly  quantitative  yields  in  a  few 
hours  at  ordinary  temperatures,  as  compared  with  heating  for  80  to 
90  hours  as  is  necessary  with  the  copper  zinc  couple.  Clemmensen 
has  recently  shown  that  ketones  and  aldehydes  are  readily  reduced  to 
hydrocarbons  by  the  zinc-mercury  couple  and  hydrochloric  acid.146 
Zelinsky  147  has  employed  the  zinc-palladium  couple  and  alcoholic  hy- 
drochloric acid  with  particularly  good  results  in  the  case  of  iodine  de- 
rivatives of  cyclohexane  and  cyclopentane.  Ordinarily,  alkyl  iodides 
give  fair  yields  of  the  paraffines  by  reducing  with  zinc  dust  in  acetic 
acid.148 

The  classical  researches  of  Sabatier  and  Senderens  have  shown 
that  ethylene  and  its  homologues  may  be  converted  into  the  corre- 
sponding hydrocarbons  by  hydrogen  in  the  presence  of  nickel  or  nickel 
oxide.  With  ethylene,  copper  appears  to  give  the  best  results.149  Ipa- 
tiev  also  employed  copper  at  300°  for  the  catalytic  hydrogenation  of 
trimethylethylene  to  pure  isopentane.150  Brochet  and  Cabaret 151 
showed  that  alpha-octene  is  readily  hydrogenated  in  the  presence  of 
active  nickel  and  at  atmospheric  pressure,  at  temperatures  as  low  as 
65°.  At  160°  p-hex#ne  and  (3-octene  are  rapidly  hydrogenated  but 
above  200°  decomposition  occurs  with  rupture  of  the  carbon  chain. 
The  methene  group  >  C  =  CH2,  as  in  substances  containing  the  allyl 
group,  are  more  readily  hydrogenated  than  other  ethylene  types.152 
Limonene,  in  the  presence  of  copper,  is  hydrogenated  to  dihydroli- 
monene,  only  the  A  8.9  group  becoming  saturated.  Platinum  black  is 
generally  not  as  effective  in  catalyzing  hydrogenation  as  nickel  and 
copper,  but,  with  this  catalyst  also,  the  methene  group  is  more  easily 
reduced  than  other  types.  For  example  at  260°  propylene  is  quickly 
reduced  to  propane  and  alpha-octene  is  rapidly  hydrogenated  at  215° 
but  trimethylethylene  and  beta-hexene  are  not  affected  under  these 
conditions.153  The  relative  ease  with  which  the  methene  group  and 

™  Compt.  rend.  IS},  473    (1902). 
"8J.  prakt.  Chem.   (2),  54,  18   (1896). 
wChem.   Zent.  1913,  II,   255. 
"T  Ber.  31,  3205    (1898). 
"8  Wislicenus,  Ann.  219,  312   (1883). 

"»  Sabatier  and  Senderens,  Compt.  rend.  130,  1559   (1900)  ;  134,  1127   (1902). 
**°Ber.  42,  2089    (1909);   43,  3387    (1910). 
181  Compt.  rend.  159,  326    (1914). 
«2  Albright,  J.  Am.   Chem.  Soc.  36,  2188    (1914). 

»« Sabatier   and    Senderens;    Compt.    rend.   124,   1358    (1897);    130,    1761    (1900); 
131,  40   (1900)  ;  134,  1127    (1902). 


THE  PARAFFINES  49 

other  olefine  types  are  hydrogenated  by  the  action  of  sodium  and  alco- 
hol is  just  the  reverse  of  the  results  noted  above.  Thus  isoeugenol, 
isosafrol  and  isoapiol  are  very  readily  hydrogenated  by  sodium  and 
alcohol  but  their  isomers,  containing  the  methene  or  allyl  group,  are 
not.154 

Although  the  catalytic  hydrogenation  or  "hardening"  of  fatty 
oils 155  has  become  of  great  industrial  importance,  unsaturated  or 
"cracked"  petroleum  distillates  have  not  been  successfully  treated  in 
this  manner,  at  least  not  industrially.156  It  is  very  difficult  to  remove 
all  of  the  sulfur  from  petroleum  distillates  and  very  small  traces  of 
this  element  are  sufficient  to  poison  the  ordinary  nickel  catalyst.  Rub- 
ber, prior  to  vulcanization  and  free  from  sulfur,  does  not  appear  to 
have  been  hydrogenated;  oily  saturated  hydrocarbons  might  result. 

Unstable  cyclic  hydrocarbons  or  naphthenes  might  be  hydrogenated 
with  rupture  of  the  ring,  after  the  manner  of  the  formation  of  isopen- 
tane  from  methylcyclobutane  by  hydrogen  and  nickel  at  200°. 157 

By  employing  relatively  high  pressures,  about  30  atmospheres,  Ber- 
gius  has  hydrogenated  fatty  oils  at  300°  without  a  catalyst.158  Whether 
or  not  unsaturated  hydrocarbons  derived  from  petroleum  would  also 
be  hydrogenated  under  these  conditions  has  not  been  determined  but 
they  are  evidently  not  affected  at  196°  and  3000  pounds  hydrogen 
pressure  per  square  inch.159  Whitaker  and  Rittman  16°  in  the  produc- 
tion of  oil  gas  at  temperatures  within  the  range  750°  to  800°  obtained 
distinct  evidence  of  hydrogenation  of  the  gaseous  defines  when  hydro- 
gen was  introduced  into  the  mixture,  particularly  when  operating  at 
increased  pressures. 

The  platinum  metals,  when  in  a  colloidal  state  of  subdivision,  are 
particularly  useful  in  hydrogenating  defines  on  a  small  scale  or  in  the 
laboratory.  Since  the  reaction  is  quantitative,  they  have  been  fre- 
quently employed  to  determine  the  number  of  olefine  bonds  in  a  sub- 
stance. The  development  of  this  method  is  due  chiefly  to  Paal,  Skita  and 
Willstatter.  Colloidal  palladium,  prepared  according  to  Paal  and  Skita, 

1MCiamician  and  Silber ;  Ber.  23,  1162.  2285   (1890)  :  Klages,  Ber.  32,  1436  (1899). 

158  Cf.  Ellis,  "The  Hydrogenation  of  Oils,"  1919 ;  Erdmann,  J.  prakt.  Chem.    (2),  91, 
469    (1915);    Paal,    Ber.    1,1,    2273    (1908);    Skita,    "Katalytische    Reduktion,"    1912; 
Sabatier,  "La  Catalyse,"  1913. 

1MCf.  Ubbelhode,  Petroleum  7,  9,  334  (1912)  ;  Brooks,  Bacon,  Padgett  and  Hum- 
phrey; J.  Ind.  &  Eng.  Chem.  7,  ISO  (1915). 

ls7Zelinsky;  J.  Soc.  Chem.  Ind.  32,  216  (1913);  Philipow,  J.  prakt.  Chem.  (2), 
95.  162  (1916). 

168  Z.   1.  angew.   Chem.  1914,  522. 

159  Brooks,  Bacon,  Padgett  and  Humphrey;  J.  Ind.  <t  Eng.  Chem.  7,  180   (1915). 
1MJ.  Ind.  &  Eng.  Chem.  6,  479   (1914). 


50        CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

is  sensitive  to  acids  but  Willstatter,161  Halse162  and  others  have  used 
colloidal  platinum  in  glacial  acetic  acid.  Under  certain  conditions 
palladium  may  also  be  used  in  acetic  acid.163 

The  distillation  of  fats  under  pressure  has  already  been  referred  to. 
The  alkali  salts  of  the  simpler  fatty  acids  yield  paraffines  when  heated 
with  caustic  alkali  or  soda-lime. 

CH3C02Na  + NaOH.  -  — >  Na2C03  +  CH4.  This  reaction  does 
not  take  place  to  any  extent  with  the  higher  fatty  acids  but  fairly 
good  yields  of  the  paraffines  are  obtained  by  heating  the  alkali  salts, 
or  soaps,  with  sodium  methylate  in  vacuo.164 

Kolbe's  electrolytic  synthesis  has  often  been  cited  but  has  been  of 
very  little  preparative  value.  Thus,  on  electrolysing  an  aqueous  solu- 
tion of  sodium  acetate  the  chief  products  are  ethane,  C02  and  hydro- 
gen.165 In  general  the  electrolysis  of  a  fatty  acid  salt  yields,  in  addi- 
tion to  the  saturated  hydrocarbon,  an  ester  and  an  olefine.  For  ex- 
ample, sodium  propionate  gives  butane,  ethylene,  ethyl  propionate,  car- 
bon dioxide  and  hydrogen.  The  higher  fatty  acids  salts  yield  a  mix- 
ture of  reaction  products  of  the  same  character.166  Aldehydes  have 
been  converted  into  the  corresponding  hydrocarbons  by  electrolytic  re- 
duction but  the  yields  are  very  poor.167 

The  well-known  method  of  Wurtz,  consisting  in  heating  alkyl  bro- 
mides or  iodides  with  sodium,  has  had  wide  application  in  laboratory 
syntheses  and  it  should  be  particularly  pointed  out  that  the  reaction 
proceeds  easily  and  with  good  yields  with  alkyl  halides  of  high 
molecular  weight.  Alkyl  chlorides  have  seldom  been  employed  for 
this  synthesis  although  Nef  and  others  have  called  attention  to  the 
fact  that  alkyl  bromides  and  particularly  iodides  have  a  much  greater 
tendency  to  decompose  to  olefines,  as  in  the  ether  reaction. 

C4H8  +  Nal  +  C2H5OH  (main  reaction) 

C4H9I  +  C2H8ONa 

V)4H9.O.CaH5  +  NaI 

The  Wlirtz  synthesis  has  also  been  useful  in  ring  closing  and  in  the  syn- 
thesis of  numerous  derivatives  of  cyclic  hydrocarbons  of  both  the  ben- 

181  Ber.  1,5,  1471    (1912). 

™j.  prakt.  Ghem.    (2)   92,  40   (1915). 

>MKelber,  Ber.  .45,  1946   (1912). 

IB*  Mai:  Ber.  22,  2133   (1889). 

'"Kolbe,  Ann.  69,  257    (1849). 

™  Peterson,  Z.  f.  Elektrochemie,  12,  141   (1906). 

'"Scheps,  Ber.  1,6,  2565   (1913). 


THE  PARAFFINES  51 

zenoid  and  non-benzenoid  type.  Normal  hexacontane,  C60H122,  the 
longest  normal  carbon  chain  compound  known,  was  made  by  means  of 
this  reaction.168  Optically  active  hydrocarbons  have  been  prepared  by 
employing  the  iodides  of  optically  active  alcohols.169 

1MHell  and  HSgle,  Ber.  22,  502   (1889). 

188  It  should  be  pointed  out  that  the  only  satisfactory  methods  of  preparing  pure 
alkyl  mono  halides  are  those  which  utilize  the  corresponding  alcohols.  To  obtain 
the  primary  halides,  or  alcohols,  recourse  is  often  had  to  the  reduction  of  fatty  acid 
esters  by  sodium  and  absolute  alcohol,  according  to  Bouveault  and  Blanc  (German 
Pat.  164,294  (1903).  The  addition  of  halogen  acid  to  alpha-olefines  gives  mainly 
secondary  halides  (R.CHX.CH2.) 


Chapter  II.     Chemical  Properties  of 
Saturated  Hydrocarbons 

(1).    Oxidation. 

The  oxidation  of  saturated  hydrocarbons  by  oxygen,  or  air,  and 
other  oxidizing  agents  is  important  in  several  respects,  for  example, — 
the  oxidation  of  lubricating  oil  in  air  compressors,  the  oxidation  and 
carbonization  of  lubricating  oils  in  automobile  or  other  types  of  inter- 
nal combustion  engines,  the  oxidation  and  resinification  of  trans- 
former oils,  the  bleaching  of  oils  by  air  and  sunlight  and  finally  the 
oxidation  of  paraffine  and  other  hydrocarbon  mixtures  to  fatty  or  soap 
forming  acids.  Unfortunately  very  little  research  has  been  carried  out 
with,  pure  specimens  of  different  types  of  hydrocarbons  with  the  re- 
sult that  we  know  very  little  regarding  their  relative  ease  of  oxida- 
tion. However  some  of  the  work  recorded,  having  had  to  do  with  com- 
mercial products,  is  of  industrial,  if  not  scientific  interest. 

As  long  ago  as  1868  Bolley  noted  that  paraffine  wax  absorbs  oxygen 
at  150°  but  he  made  no  particular  study  of  the  matter.1  Others  noted 
that  when  air  is  passed  through  hot  mineral  oils  small  quantities  of 
acetic  and  other  simple  fatty 'acids  are  formed.2  Holde  noted  the  oxi- 
dation and  thickening  of  mineral  lubricating  oils  when  heated  in  thin 
layers  for  10  hours  at  100°  3  and  in  1896  Byerly  and  Mabery  described 
their  now  well-known  process  of  manufacturing  "artificial  asphalt"  by 
blowing  air  through  heavy  high  boiling  petroleum  residues  for  four  to 
five  days  at  about  230°.  The  reaction  is  strongly  exothermic  and  the 
temperature  may  rise  to  300°-400°  at  the  end  of  the  operation.  Water 
is  formed  during  the  process  and  very  little  oxygen  remains  in  the 
final  product,  typical  specimens  showing  1.90  to  2.20  per  cent  oxygen. 
The  bromine  absorption  values  of  the  product  are  also  low,  ordinarily 
amounting  to  14.0  to  19.0.  The  hardness  and  other  physical  properties 
of  this  asphalt  would  seem  to  indicate  that  considerable  polymerization 
or  condensation  takes  place  during  the  process.  Intermediate  products 

1  Z.  f.   Chemie,  1868,  500. 

2Zaloziecki,  Z.  anyeio.  Chem.  1891,  416;  Engler  &  Bock,  Chem.  Ztg.  16,  592   (1892). 

« J.  Soc.  Chem.  Ind.  13,  G68   (1894)  ;  Ik,  174   (1895). 

52 


CHEMICAL  PROPERTIES  OF  SATURATED  HYDROCARBONS       53 

containing  oxygen  are  undoubtedly  formed,  which  may  condense  with 
the  elimination  of  the  water  which  is  always  observed.  At  lower  tem- 
peratures oxidation  by  air  has  a  markedly  different  result:  oxygen  is 
absorbed  forming  fatty  or  naphthenic  acids  and  some  resinous  matter. 
It  would  appear  that  at  the  higher  temperatures  employed  by  Byerly 
and  Mabery  the  oxidation  products  first  formed,  conceivably  alcohols, 
aldehydes  and  ketones,  condense  with  the  elimination  of  water,  but  at 
lower  temperatures,  these  primary  oxidation  products  are  subjected 
to  further  oxidation  to  fatty  or  naphthenic  acids. 

According  to  Worrall  and  Southcombe 4  lubricating  oil  may  be 
heated  to  750°  F.  in  the  presence  of  steam  without  causing  resinifica- 
tion  or  other  chemical  change  (although  it  may  be  noted  that  this  is 
approximately  the  temperature  employed  by  Burton  for  cracking  heavy 
oils  to  gasoline). 

The  resinous  oxidation  product  which  is  slowly  formed  on  heating 
mineral  oils  to  100°-150°  in  contact  with  air,  may  partially  be  pre- 
cipitated by  petroleum  ether.  The  resin  behaves  as  an  acid  and  may 
be  removed  by  shaking  out  with  alcoholic  alkali.  Kissling  5  associates 
this  resin  with  carbonization  and  for  testing  purposes  has  proposed  the 
determination  of  "tar  numbers"  and  "coke  numbers"  of  lubricating  oils, 
after  heating  to  150°  for  50  hours  under  standardized  conditions.6 

Transformer  oils  deteriorate  by  air  oxidation  particularly  when  the 
oil  becomes  heated  as  is  usually  the  case  when  in  service.  As  is  indi- 
cated above,  water,  carbon  dioxide,  acid  resinous  material  and  simple 
fatty  acids  are  formed.  The  latter  are  sometimes  found  in  much  used 
transformer  oils  in  the  form  of  iron  or  copper  soaps,  small  quantities 
of  which  remain  dissolved  in  the  oil,  and  also  in  the  form  of  insoluble 
basic  salts  or  "sludge."  Digby  7  states  that  these  metallic  soaps  prob- 
ably act  catalytically  in  promoting  the  oxidation.  Waters  states  that 
"These  substances  (resinous)  are  oxidation  products,  and  are  most  effi- 
cient oxygen  carriers."  .  .  .  "By  heat  they  become  polymerized  and 
changed  into  asphaltic  matter."  "If  they  are  not  removed  (as  by  fil- 
tration through  fuller's  earth  or  bone  black)  heating  the  oil  in  the  air 
produces  more  asphalt  than  would  otherwise  be  the  case."  A  particu- 
lar specimen  of  a  typical  resinous  deposit  showed  76.0  per  cent  carbon 
and  7.1  per  cent  hydrogen.  The  practical  importance  of  the  matter  is 
apparent  from  the  fact  that  0.06  per  cent  of  water  in  a  transformer  oil 

*/.  Soc.   Chem.  Ind.  2J,  315    (1905). 

•Chem.  Ztg.  30,  932   (1906)  ;  SI,  328   (1907)  ;  52,  938   (1908)  ;  SS,  521,   (1909). 
•Compare  Waters,  U.  S.  Bur.  Standards  Bull.  7,  365   (1911)  ;  Circular  99  (1920). 
7  J.  Inst.  Elec.  Eng.  53,  146  (1915). 


54        CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

reduces  its  dielectric  resistance  to  about  50  per  cent  of  the  value  for  the 
same  oil  when  dry.8  Pure  paraffine  oil  can  hold  this  amount  of  water 
in  solution  and  commercial  transformer  oils  are  able  to  hold  in  solution 
three  to  four  times  this  proportion  of  water.  Waters  9  noted  the  forma- 
tion of  0.89  per  cent  of  water  in  a  lubricating  oil  exposed  to  air  and 
light  for  22  days.  Light,  however,  accelerates  oxidation  by  air.  The 
above  observations  were  carried  out  with  refined  commercial  oils,  but 
small  percentages  of  olefine  hydrocarbons  were  undoubtedly  present 
in  all  the  specimens  investigated,  since  refining  as  ordinarily  carried 
out  with  concentrated  sulfuric  acid  does  not  remove  all  the  olefines, 
the  polymers  thereby  formed  remaining  in  the  oil.  Generally  olefines 
are  more  rapidly  oxidized  by  air  than  saturated  hydrocarbons,  but 
Waters  found  that,  of  several  oils  examined  by  him,  the  one  having 
the  largest  per  cent  of  unsaturated  hydrocarbons,  as  indicated  by  the 
iodine  number  and  Maumene  test,  showed  the  least  oxidation.  Wa- 
ters suggests  that  these  differences  may  have  been  due  to  greater 
amounts  of  catalysts  or  oxygen  carriers  in  the  oxidized  oils.  The  con- 
clusion which  may  be  drawn,  however,  is  that  factors  other  than  the 
presence  of  olefines  are  of  primary  importance.  On  account  of  its  de- 
composing action  on  resins  and  similar  oxidized  material,  and  its  ener- 
getic action  on  unsaturated  hydrocarbons,  it  is  possible  that  oils  re- 
fined by  anhydrous  aluminum  chloride  would  be  more  stable  and  more 
resistant  to  oxidation  in  service  as  transformer  oils  than  those  oils 
which  have  been  refined  in  the  usual  way  with  sulfuric  acid. 

Although  the  accelerating  effect  of  sunlight  on  oxidation  by  air  is 
taken  advantage  of  in  the  industrial  sun  bleaching  of  mineral  oils,  no 
study  of  individual  hydrocarbons  appears  to  have  been  made.  Cia- 
mician  and  Silber  10  succeeded  in  oxidizing  the  methyl  groups  of  toluene 
and  xylene  to  the  corresponding  acids  by  air  under  the  influence  of 
sunlight.  In  the  case  of  non-benzenoid  hydrocarbons  the  group 
R 

>CH2  and  R3CH,  would  probably  be  oxidized  rather  than  methyl 
R 
groups. 

It  has  been  shown  by  the  well-known  work  of  Engler  and  Weiss- 
berg  "  that  organic  substances,  which  alone  are  not  appreciably  af- 
fected by  air  or  oxygen,  may  readily  be  oxidized  in  the  presence  of  a 

8  The   method   advocated   by   C.   E.   Skinner,   of   purifying   old   transformer   oils   by 
quick-lime,  removes  both  water  and  fatty  acids. 
"Loc.   cit. 

™Ber.  .45,  38  (1912). 
"Vorgange   der   Autoxydation,    Brunswick,    1904. 


CHEMICAL  PROPERTIES  OF  SATURATED  HYDROCARBONS       55 

second  substance  which  is  capable  of  direct  oxidation.  They  have 
shown  that  the  latter  class  of  substances  form  peroxides  and  their 
hypothesis  is  that  these  peroxides  may  then  effect  the  oxidation  of 
substances  which  by  themselves  are  inert  to  oxygen.  Thus  paraffine 
wax  is  only  very  slowly  affected  by  air  or  oxygen  at  150°  but  the 
oxidation  is  very  much  accelerated  if  a  small  quantity  of  previously 
oxidized  material  is  introduced.  Unsaturated  hydrocarbons  which  are 
capable  of  forming  peroxides,  according  to  Engler's  theory 
RCH  =  CHRi  +  02 >  RCH CHR± 

v 

may  in  this  way  bring  about  the  oxidation  of  saturated  hydrocarbons. 
Based  upon  this  theory  the  oxidation  of  paraffine  has  been  brought 
about  by  first  chlorinating  at  160°  followed  by  decomposition  of 
these  chlorides  by  heating  to  300°  and  then  oxidizing  to  fatty  acids.12 
Organic  peroxides  are  decomposed  by  moisture  which  explains  the 
finding  of  Charitschkoff  mentioned  above.  Thus  linseed  oil  shows 
greater  increase  in  weight  on  "drying"  in  dry  air  than  in  moist  air,  at 
least  during  the  first  few  days'  exposure. 

The  oxidation  of  paraffine  wax  by  air  at  120°  and  150°  was  noted 
as  long  ago  as  1868,13  but  under  the  stress  of  the  conditions  prevailing 
in  Central  Europe  during  the  war  intensive  research  on  the  synthesis 
of  fatty  acids  was  carried  out  by  a  special  commission  of  the  German 
government,  presided  over  by  C.  Engler.  Numerous  researches  of  the 
same  character  were  undertaken  by  private  concerns  and  a  number  of 
patents  and  published  papers  have  recently  appeared  dealing  with  this 
subject.  The  statements  of  different  investigators  regarding  the  ef- 
fect of  metallic  oxides  and  other  substances  introduced  as  catalysts 
is  very  contradictory  but  the  most  complete  results  published  up  to  the 
present  time  indicate  that  the  best  yields  are  obtained  without  the 
addition  of  any  catalytic  material  other  than  a  small  amount  of  pre- 
viously oxidized  material  added  to  initiate  the  reaction.14  The  use  of 
air  under  pressure  accelerates  the  oxidation  15  but  the  substitution  of 
oxygen  for  air  causes  the  reaction  to  proceed  too  rapidly  and  per- 
oxides are  formed  and  accumulate  to  such  an  extent  that  violent  ex-, 
plosions  are  apt  to  occur.  When  the  oxidation  is  slowly  and  carefully 
carried  out  waxy  esters  of  the  fatty  acids  and  higher  alcohols,  formed 

12  Schaarschmidt  &  Thiele,  Ber.  53B.   2128   (1920). 

lsBolly  &  Tuchschmidt.  Z.  f.  Chemie.  1868,  500;  Jazukowitsch,  Ber.  8,  768  (1875). 
"Griin.     Ulbrich   &   Wirth,   Ber.  5SB.   987    (1920). 

18Loffl,  Chem.  Ztg.  kk,  561   (1920).     Schneider,  J.  Soc.  OJtem.  Ind.  40,  141A.   (1921), 
uses  tubular  retorts  and  air  under  70  atmospheres  pressure. 


56        CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

evidently  as  intermediate  products,  may  be  isolated  from  the  oxidized 
mixture.16  The  oxidation  to  fatty  acids,  with  yields  amounting  to 
approximately  86  per  cent  of  the  theory,  takes  place  in  a  remarkably 
short  time,  this  yield  being  obtainable  in  12  hours  at  160°  in  the  ab- 
sence of  catalysts.  In  a  normal  oxidation  the  peroxides  noted  above 
are  decomposed,  probably  assisting  in  the  oxidation  in  the  manner  indi- 
cated by  Engler  and  Weissberg.  Carbon  dioxide,  formic,  acetic  and 
other  simple,  volatile  fatty  acids  are  formed  and  the  yield  of  these  ap- 
pears to  vary  within  wide  limits,  one  of  the  "tricks"  of  the  process 
being  so  to  conduct  the  oxidation  that  only  small  proportions  of  these 
malodorous  acids  are  formed.  Presumably  these  volatile  acids  are 
removed  by  blowing  with  live  steam,  the  residue  having  an  acid  num- 
ber of  180  to  200,  being  then  neutralized  by  alkali  and  the  unsaponifi- 
able  portion  returned  for  further  oxidation.  According  to  Loffl 17  acids 
satisfactory  for  soap  manufacture  have  not  yet  been  obtained,  the  addi- 
tion of  10  to  20  per  cent  of  cocoanut  or  palm  oil  being  necessary  to 
produce  a  soap  of  the  desired  detergent  qualities.  According  to  Loffl 
120°  is  the  best  working  temperature  with  air  under  about  45  pounds 
pressure.  The  presence  of  water,  continually  introduced  with  the  air 
in  the  form  of  steam,  favors  the  production  of  the  higher  fatty  acids 
and  in  the  absence  of  water  or  its  removal  as  fast  as  formed  the  product 
is  highly  colored  and  partially  resinified.  As  is  usual  in  such  cases  a 
large  number  of  special  patents  have  appeared  18  claiming  special  ad- 
vantages for  various  catalysts  and  other  minor  details  of  operation 
although  the  general  process  seems  to  have  been  broadly  covered  by 
previous  publications,  particularly  the  patent  of  Schaal.19  Most  of 
the  published  work  on  this  subject  has  had  to  do  with  the  oxidation  of 
paraffine  wax,  probably  with  the  idea  of  manufacturing  fatty  acids 
identical  with  fatty  acids  occurring  in  natural  fats  and  oils,  but  in  view 
of  the  much  larger  quantities  of  liquid  naphthenic  hydrocarbons  of 
fifteen  to  twenty  carbon  atoms  (present  in  kerosene  and  the  inter- 
mediate or  fuel  oil  distillates)  and  the  lower  cost  of  such  material,  it 
would  seem  highly  desirable  to  study  the  oxidation  of  such  oils  under 
similar  conditions.  Although  the  carboxylic  acid  derivatives  of  the 
naphthenes  as  exemplified  by  the  Russian  naphthenic  acids,  have  ob- 
jectionable and  very  persistent  odors,  it  is  probable  that  these  cyclic 

18Griin.  Ulbrich  &  Wirth.  Ber.  53B.  987    (1920). 
"Loc.  cit. 

18  Pardubitzer  Fabr.  Akt.  Ges.   f.  Mineralolindustrie,   Brit.  Pat.   131,301  ;   131,302  ; 
131,303;  Schmidt,  Brit.  Pat.  109,386   (1907)  ;  Cf.  also  Fischer  &  Scheider,  Ber.  53,  923 
(1920)  ;   Kelber,   Ber.  53,  66    (1920)  ;   Bergman,   Z.  f.   angew.   Chem.  31,  I,   69    (1918)  ; 
Holde,  Chem.  Ztg.  78,  447   (1920)  ;  Plauson,  Brit.  Pat.  156,141    (1919). 

19  Schaal,  German  Pat.  32,  705. 


CHEMICAL  PROPERTIES  OF  SATURATED  HYDROCARBONS      57 

hydrocarbons  would  be  decomposed  by  oxidation  to  open  chain  acids. 
Montan  wax  is  more  resistant  to  air  oxidation  than  paraffine  wax.20 

Harries  has  applied  his  well-known  method  of  ozonization  to  highly 
unsaturated  oils  such  as  the  oily  distillates  obtained  by  the  low  tem- 
perature carbonization  of  coal  and  lignite. 

When  saturated  hydrocarbons  are  burned  with  insufficient  air  for 
complete  combustion,  a  little  formaldehyde  is  formed.  From  a  hexane 
fraction  and  isopentane  Stepski 21  obtained  water,  carbon  dioxide,  for- 
maldehyde, ethylene  and  small  quantities  of  propylene,  butylene  and 
amylenes.  The  yields  of  formaldehyde  and  ethylene  by  known  meth- 
ods are  too  small  for  the  process  to  be  of  industrial  value. 

The  action  of  chemical  oxidizing  agents  on  saturated  hydrocarbons 
shows  that  certain  structures  are  more  easily  oxidized  than  others. 
Zelinsky  and  Zelikow 22  have  noted  that  hydrocarbons  of  the  type 

R 

>CHR 
R 

for  example  (C,H5)2CH.CH3  are  readily  oxidized  by  one  per  cent 
potassium  permanganate  solution.  As  contrasted  with  this,  methane 
and  ethane  are  only  very  slowly  oxidized  by  five  per  cent  perman- 
ganate solutions.23  The  hydrocarbon  2 . 6-dimethyloctane  is  fairly  sta- 
ble to  permanganate  at  100°  but  in  the  presence  of  unsaturated  hydro- 
carbons (menthene)  the  dimethyloctane  is  oxidized  rather  rapidly  even 
at  50°. -4  (3-Butylhexane  is  rapidly  oxidized  by  alkaline  permanganate 
solution  at  80°  to  90°,  but  the  only  oxida.tion  products  which  can  be 
detected  are  carbon  dioxide  and  formic  acid:  by  oxidizing  it  at  25°  a 
very  small  amount  of  butyric  acid  can  be  recognized.25  Hydrocarbons 
of  the  type  R1R2R3CH  are  also  very  easily  oxidized  by  concentrated 
nitric  acid,  Sp.  Gr.  1.53  but  normal  hydrocarbons,  at  ordinary  tempera- 
tures are  only  very  slowly  acted  upon.  Less  concentrated  acid,  Sp.  Gr. 
1.4226  gives  a  mixture  of  nitro  derivatives  and  oxidation  products  of 
the  normal  hydrocarbons,  and  the  least  oxidation  and  maximum  yields 
of  nitro  derivatives  are  obtained  by  heating,  preferably  in  sealed  tubes, 
with  dilute  nitric  acid  of  1.075  specific  gravity.27  Paraffine  wax  is 
slowly  oxidized  by  nitrogen  peroxide 28  at  temperatures  within  the 

20  Schneider,  J.   Soc.  Chem.  Ind.  W,  140A.    (1921). 

^Monatsh.  23,  773    (1902). 

MBer.  34,  2865   (1901). 

23  V.  Meyer  &  Saam,  Ber.  SO,  1438   (1897). 

"Kishner,  J.  Russ.  1,5,  1788    (1913). 

"Levene  &  Cretcher,  J.  Biol.  Chem.  33,  505   (1918). 

"Worstall,  Am.  Chem.  J.  20,  209   (1898)  ;  21,  213   (1899). 

27  Konowalow,  /.  Russ.  Phys.-Chem.  Soc.  27,  418  (1895)  ;  Chem.  Zentr.  1900,  I,  975. 

28Granacher,  Helv.   Chim,   Acta.  3,  721    (1921). 


58        CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

range  110°-150°.  A  mixture  of  fatty  acids,  from  acetic  upwards  in 
the  series,  is  produced.  Alkaline  solutions  of  these  fatty  acids  are 
red  in  color  due  to  the  presence  of  nitro  compounds.  As  might  be 
expected  the  results  of  oxidizing  with  nitric  acid  and  by  permanganate 
are  quite  different.  The  fatty  acids,  with  the  exception  of  acetic  acid, 
are  almost  invariably  more  readily  oxidized  than  the  hydrocarbons 
and  large  yields  of  the  former  could,  therefore,  hardly  be  expected 
among  the  reaction  products.  Prshevalski 29  has  shown  that  the  higher 
normal  fatty  acids  are  oxidized  by  permanganate  at  two  points,  i.  e., 
at  the  carbon  atom  adjacent  to  the  end  methyl  group  and  also  at  the 
carbon  atom  adjacent  to  the  carboxyl  group.  Isobutyric  acid  is  oxi- 
dized to  the  oxy  acid  (CH3)2  =  C  —  C02H  but  with  hydrocarbons  the 


molecules  are  completely  broken  up.  Nitric  acid,  however,  forms  a 
series  of  fatty  acids  and  dicarboxylic  acids.  In  addition  to  carbon 
dioxide  and  the  simpler  fatty  acids,  oxalic,  succinic  and  adipic  acids 
have  been  observed  among  the  oxidation  products.30  Oxidation  by 
nitric  acid  may  become  violent  at  100°. 31 

Chromyl  chloride,  Cr02Cl2  has  been  employed  by  Etard  32  and  by 
Miller  and  Rohde  33  to  oxidize  the  aliphatic  side  chains  of  benzene  de- 
rivatives. Toluene  yields  benzaldehyde  and  ethyl  benzene  is  oxidized 
mainly  at  the  CH2  group  to  form  acetophenone.  This  interesting  re- 
action, however,  has  not  been  applied  to  the  study  of  the  paraffine  hy- 
drocarbons, although  Etard  oxidized  hexane  to  a  chloroketone  and 
Schulz  34  treated  a  number  of  light  fractions  from  Boryslaw  petro- 
leum with  chromyl  chloride,  obtaining  ketone  mixtures  which  were 
not  further  studied  or  identified. 

Sulfur. 

Sulfur  reacts  with  paraffines  and  naphthenes  on  heating,  hydrogen 
sulfide  being  evolved,  but  little  is  known  regarding  the  other  products 
formed.  Galletly  35  first  noted  that  hydrogen  sulfide  could  conven- 
iently be  prepared  by  heating  sulfur  and  paraffine  wax.  Somewhat 

29  J.  Chem.  Soc.  Abs.  1913,  I,  1151. 

80  Markownikow,  Chem.  Zentr.  1899,  I.  1064;  II,  472.  473;  Ber.  82,  144  (1899); 
J.  prakt.  Chem.  (2),  59,  556  (1899). 

31  Young  &  Francis,  J.   Cliem.  Soc.  73,  928    (1S98). 

32Compt.  rend.  90,  534    (1880). 

33  Ber.  23,   1070    (1890). 

3*Petr.  6,  189. 

36  Chem.  News  2!lt  107   (1871). 


CHEMICAL  PROPERTIES  OF  SATURATED  HYDROCARBONS      59 

later  Lidoff  36  made  hydrogen  sulfide  by  passing  naphtha  vapors  into 
sulfur  at  350°  to  400°.  Friedmann  37  isolated  thiocresol  as  one  of  the 
reaction  products  of  sulfur  and  methylcyclohexane  but  was  unable  to 
isolate  benzene  from  the  reaction  product  of  sulfur  and  hexane.  He 
isolated  dinitrobenzene  after  nitrating  the  product,  which  Friedman 
states  is  possibly  due  to  the  initial  formation  of  cyclohexadiene  which 
on  nitration  is  converted  into  dinitrobenzene.  Guiselin  38  noted  that 
"benzine"  dissolves  about  0.5%  sulfur  at  20°,  the  higher  boiling  distil- 
lates dissolving  somewhat  more  than  this.  Raffo  and  Rossi 39  state 
that  pyridine  catalyzes  the  evolution  of  hydrogen  sulfide  when  hydro- 
carbons and  sulfur  are  heated.  Markownikow 40  obtained  xylene  from 
an  octonaphthene.  Normal  hexane  41  is  practically  inert  to  sulfur  at 
210°  but  parafrme  wax  or  heavy  greases  react  vigorously  at  this  tem- 
perature. Prothiere  42  obtained  48  liters  of  hydrogen  sulfide  from  70 
grams  of  sulfur  and  30  grams  of  vaseline.  It  has  occasionally  been 
suggested  that  sulfur  might  be  employed  to  remove  hydrogen  from 
paraffines  or  petroleum  oils  to  form  highly  unsaturated  oils  having 
several  double  bonds  and  such  products  presumably  would  have  the 
general  character  of  drying  oils.  However,  since  sulfur  reacts  much 
more  readily  with  the  ethylene  bond  than  it  does  upon  saturated  hydro- 
carbons, the  result  is  a  certain  amount  of  carbonized  material  and  un- 
changed oil  or  paraffine,  a  hydrocarbon  molecule  once  being  reacted 
upon  then  rapidly  reacting  with  more  sulfur  to  form  a  series  of  prod- 
ucts of  unknown  character,  the  final  product  resembling  asphalt,  or 
when  strongly  heated,  petroleum  coke.  When  added  to  heavy  residuum 
and  blown  with  air,  sulfur  has  the  effect  of  giving  a  markedly  harder 
so-called  asphalt.43  Sulfur  derivatives  frequently  exhibit  a  much 
greater  tendency  to  polymerize  than  their  oxygen  analogues  and  this 
fact  may  account  for  the  greater  hardness,  i.  e.,  greater  degree  of  poly- 
merization, of  asphalts  made  from  residuum  high  in  sulfur;  for  example, 
that  from  Mexican  petroleum.  Under  these  conditions  a  large  part 
of  the  sulfur  contained  in  or  added  to  the  original  residuum  remains 
in  the  final  product.  The  following  results  obtained  by  blowing  a 
residuum,  12°  Be,  from  Texas  Gulf  Coast  petroleum,  with  air  are  rep- 
resentative. 

M  Chem.  Zentr.  1882,  22. 

"J.  Chem.  Soc.  A  6*.  1917.  I,  13. 

88  Petroleum,  1913,  1309. 

*gGcusz.  Chim.  Ital.  44,  104   (1914). 

*>Ber.  1887,  1850. 

41  Spanier,  Dissertation,  Karlsruhe,  1910 

42  Ohem.  Zentr.  1903,  I.  492. 

43  Brooks  &  Humphrey,  J.  Ind.  d  Eng.  Chem.  8,  746   (1917). 


60        CHEMISTRY  OF  THE  NOtf-BENZENOJD  HYDROCARBONS 

EFFECT  OF  SULFUR  ON  HARDNESS  OF  BLOWN  ARTIFICIAL  ASPHALT. 

Sulfur  Temp,  Hours  Penetration 

added  %              °C  Blown  mm.*  Flowing-point  °C 

(1)  None               210  14  Too  soft  for  measurement 

(2)  4.0                   210  10  61  73 

(3)  6.0                    210  10  28  109 

(4)  8.0                   210  10  17  148 

(5)  8.0                   215  10  13  167 
*Penetration  of  No.  2  needle,  100  gram  weight  for  5  seconds  at  25°C. 

Nitration  of  Non-Benzenoid  Hydrocarbons. 

Probably  on  account  of  the  great  industrial  importance  of  nitro 
derivatives  in  the  aromatic  series,  the  nitration  of  non-benzenoid  hy- 
drocarbons of  open  chain  and  cyclic  structure  has  been  relatively  little 
investigated.  Oxidation  by  nitric  acid  generally  takes  place  to  a 
much  greater  extent  in  the  case  of  saturated  non-benzenoid  hydro- 
carbons than  with  those  of  the  aromatic  series  and  the  relative  yields 
of  oxidation  and  nitration  products  depend  upon  many  factors,  chief 
of  which  are  the  concentration  of  the  nitric  acid  used  and  the  tempera- 
ture. The  constitution  of  the  hydrocarbon  is  also  of  importance.  The 
use  of  dilute  nitric  acid,  Specific  Gravity  1.025  to  1.075,  at  115°  to 
125°,  constitutes  a  method  whereby  fairly  good  yields  of  nitro-deriva- 
tives  may  be  obtained.  The  reaction  is  usually  carried  out  in  sealed 
tubes  in  the  case  of  very  volatile  hydrocarbons,  but  easily  nitrated 
hydrocarbons  are  preferably  heated  with  the  dilute  acid  under  a  re- 
flux condenser.  These  methods  are  due  chiefly  to  Konowalow,44  and  to 
Markownikow.45  Concentrated  or  fuming  nitric  acid  or  nitric-sulfuric 
acid  nitrating  mixture  gives  mostly  oxidation  products.  Hydrocarbons 
containing  a  tertiary  hydrogen  atom,  R3CH,  are  most  easily  nitrated; 
for  example,  2,  5-dimethylhexane  yields  a  dinitro  derivative,46  which  is 
insoluble  in  alkali  solution  and  which  exhibits  the  exceptional  property 
of  being  crystalline,  melting  at  124°-125°. 


CH3  -  C  -  CH2CH2  -  C  -  CH3  --  >  CH3  -  C  -  CH2CH2  -  C  -  CH3 

H  H  N02  N02 

The  hydrocarbon  2,  6-dimethylheptane  similarly  gives  the  tertiary 
nitro  derivative,  which  is  easily  separated  from  the  relatively  small 
amount  of  primary  and  secondary  nitro-compounds  by  the  solubility 

"Ber.  25,  1244   (1892)  ;  28,  1852   (1895)  ;  29,  2199   (1896). 

*8J.  prakt.  Cliem.    (2)   59,  564   (1899). 

46Konowalow,  J.  Russ.  Phys.-Chem.  Boc.  38,  I,  109   (1906). 


CHEMICAL  PROPERTIES  OF  SATURATED  HYDROCARBONS      61 

of  the  latter  two  classes  in  aqueous  alkali.  This  solubility  in  alkali  of 
nitro  derivatives  of  the  types  CH.N02  and  —  CH2N02  is  a  general 
property  common  to  all  nitro  derivatives  of  these  types,47  the  alkali 
salts  probably  having  the  constitution  represented  by  the  formulae 

0  0 

—  CH^N 


and 

ONa  ONa 

The  hydrocarbon  2,7-dimethyloctane  yields,  with  concentrated  nitric 
acid,  the  primary  nitro  derivatives,  but  with  dilute  acid  gives  2,7- 
dinitro-,  2,7-dimethyloctane,  melting  point  101.5°-102°. 

As  contrasted  with  the  above  hydrocarbons,  containing  tertiary 
hydrogen,  the  hydrocarbons 

(CH3)3C.CH2CH3  and  (CH3)3C.CH2CH2CH3 

are  nitrated  only  with  difficulty;  in  fact,  the  former  can  be  purified 
from  isomeric  hydrocarbons  by  repeatedly  nitrating  the  fraction  boil- 
ing at  48°-51°.48  When  these  hydrocarbons  are  nitrated,  the  nitro- 
group  is  attached  to  the  carbon  atom  next  to  the  (CH3)3.C  group.  The 
normal  paraffines  are  also  nitrated  much  less  readily  than  their  branch 
chain  isomers.  Di-isopropyl  (CH3)2CH.CH(CH3)2  reacts  very  ener- 
getically with  nitric  acid  at  20°,  but  not  with  the  nitric-sulfuric  acid 
nitrating  mixture  commonly  employed  to  nitrate  benzene. 

That  saturated  non-benzenoid  hydrocarbons  are  more  easily  ni- 
trated by  dilute  nitric  acid  than  the  benzene  ring  is  shown  by  a  number 
of  examples.  Phenylcyclohexane  is  nitrated  in  the  cyclohexane,  not 
in  the  benzene  ring.49  Here  also  nitration  takes  place  at  the  tertiary 
hydrogen  atom  yielding  1  -nitro-  1-pheny  Icy  clohexane 

CH2  —  CH2          N02 
H2C  C 

CH2  —  CH2          C6H8 

O£/io-xylene  with  dilute  nitric  acid,  Sp.  Gr.  1.075  at  110°  gives 
o-tolylnitromethane,50  which  like  all  primary  nitro  compounds  easily 
forms  alkali  salts.  Dilution  of  nitric  acid  with  acetic  acid  has  practi- 

«  Cf.  Nef.  "Constitution  of  the  Nitroparaffines."  Ann.  270,  331  (1892)  ;  280,  263 
(1894). 

«  Markownikow.  Chem.  Zentr.  1S99,  II,  472  :  Ber.  82,  1446,  (1899)  :  Ber.  S3,  1908 
(1900). 

"Kursanoff.  J.  Chem.  Soc.  Abs.  J907,  I,  599. 

"Konowalow.  J.  Chem.  Soc.  Aba.  1905,  I,  762. 


62         CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

cally  the  same  effect  as  dilution  with  water;  dilution  and  heating  di- 
rects the  nitration  chiefly  to  the  side  chain,  forming  nitro  derivatives 
and  also  acids  by  oxidation.  In  accord  with  the  above  observations 
1 . 2-dipheny Ipropane  gives  the  primary  nitro  derivative  rather  than 
substitution  in  the  benzene  ring,  C6H5CH2CH(C6H5)  .CH2NO2.  Ben- 
zoyl  nitrate  is  a  reagent,  which  with  benzene,  toluene,  phenol,  anisole, 
naphthol,  coumarine  and  thiophene  gives  nitro  derivatives  very 
smoothly,  but  when  several  methyl  groups  are  present,  nitration  of  a 
methyl  group  takes  place,  as  in  durene.51 

C6H2(CH3)4-     ~>C6H2(CH3)3.CH2N02 

In  nitrating  p-cymene  the  isopropyl  group  is  attacked  at  the  ter- 
tiary hydrogen  atom  forming  p-methylacetophenone,  by  oxidation,  un- 
less special  precautions  are  taken,52  advantage  being  taken  of  the  fact 
that  the  paraffines  are  but  little  affected  by  nitric-sulfuric  acid  nitrat- 
ing mixture. 

The  aliphatic  ketones  are  much  more  reactive  to  nitric  acid  than 
the  hydrocarbons.  Nitric  acid,  specific  gravity  1.38,  yields  a  mixture 
of  products  of  which  dinitro  ketones  and  dinitro  hydrocarbon  deriva- 
tives are  conspicuous,  the  formation  of  these  products  being  accom- 
panied by  splitting  of  the  carbon  structure,  probably  as  indicated  by 
the  reaction, 

(a)  RCO .  CH2R' >  RCO .  C  (N02)  2R' 

(b)  R .  CO .  C  (N02)  2R'  +  H20 >  RCOOH  +  R'CH  (N02)  2 

Menthone  is  readily  nitrated  by  dilute  nitric  acid  to  the  mononitro 
derivative 53 


=  0  =0 


81  WillstKtter  &  Kubli.  Ber.  W,  4152   (1909). 

82  Andrews,  J.  Ind.  d  Eng.  Ctiem.  10,  453   (1918). 

M  Konowalow,  Ber.  26,  Ref.  878    (1893)  ;  28,  Ref.  1054   (1895) 


CHEMICAL  PROPERTIES  OF  SATURATED  HYDROCARBONS      63 

Suflonation 

The  difference  in  the  ease  with  which  benzenoid  hydrocarbons  on 
the  one  hand  and  paraffine  or  non-benzenoid  hydrocarbons  on  the  other 
are  sulfonated  is  not  as  great  as  is  commonly  supposed.  Although 
data  with  respect  to  hydrocarbons  of  known  character  and  purity  are 
extremely  meager,  Worstall 54  showed  that  n .  hexane,  n .  heptane,  and 
n. octane  are  readily  sulfonated  by  fuming  sulfuric  acid  at  the  tem- 
perature of  a  water  bath  and  Markownikow  55  states  that  naphthenes 
also  are  reacted  upon  by  fuming  sulfuric  acid,  both  sulfonation  and  oxi- 
dation taking  place.  Paraffine  wax  is  attacked  by  warm  fuming  sul- 
furic acid  but  oxidation  rather  than  sulfonation  is  the  result.56  Oxida- 
tion occurs  with  fuming  acid  and  saturated  hydrocarbons  to  a  much 
greater  extent  than  in  the  case  of  benzene  and  its  derivatives.  Hy- 
drocarbons containing  a  tertiary  hydrogen  group  as  in  di-isopropyl 
(CH3)2CH.CH(CH3)2  are  much  more  readily  sulfonated  and  oxi- 
dized than  normal  paraffine  hydrocarbons  and  it  is  possible  that  the 
large  losses  experienced  in  the  refining  of  lubricating  oils  by  concen- 
trated sulfuric  acid  are  in  part  due  to  the  sulfonation  and  oxidation  of 
branched  chain  hydrocarbons. 

Halides.    Preparation  and  Properties. 

In  the  following  pages  the  methods  of  preparation  and  more  par- 
ticularly the  properties  of  the  simpler  alkyl  halides  will  be  discussed. 
Very  little  work  has  been  done  with  fluorine  derivatives,  and  such 
information  as  we  have  does  not  indicate  that  fluorine  derivatives 
possess  particularly  interesting  or  valuable  properties.  When  writing 
of  the  halogen  derivatives,  it  will,  therefore,  be  understood  that  gen- 
erally chlorides,  bromides  or  iodides  only  are  meant. 

Our  knowledge  of  the  simpler  alkyl  halides,  especially  chlorides, 
has  recently  been  much  extended  by  the  development  of  synthetic 
rubber,  and  this,  it  may  be  noted,  is  coincident  with  the  production 
of  enormous  quantities  of  electrolytic  chlorine  at  very  low  cost.  Cheap 
chlorine  makes  many  processes  industrially  possible,  which  heretofore 
have  been  only  of  theoretical  interest. 

The  conditions  for  the  chlorination  of  methane  have  been  noted 
(page  79).  Chlorine  reacts  readily  with  butane  and  pentane  and  the 
higher  paraffines  in  the  cold  and  in  diffused  daylight.  It  has  repeatedly 
been  observed  that  in  chlorinating  petroleum  ether  a  sluggish  so-called 
induction  period  is  first  noted.  The  chlorine  dissolves  in  the  hydro- 

"Am.  Chem.  J.  23,  654   (1898). 

85  J.  Russ.  Phys.-Ctiem.  Soc.  1892,  141. 

»  Michailescu  &  Istrati.  Bull.  Soc.  Sci.  Bucharest.  13,  143. 


64        CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

carbon  apparently  without  reacting,  but,  after  a  few  minutes,  the  color 
is  suddenly  discharged  and  the  reaction  thereafter  proceeds  very 
rapidly.  An  excellent  example  of  this  peculiar  induction  period  57  has 
been  observed  in  the  case  of  brominating  cyclohexanone  and  1, 1-di- 
methylhexanone(3).  Catalysts  are  not  necessary,  although  the  pres- 
ence of  moisture  is  distinctly  advantageous  in  the  case  of  the  more 
volatile  hydrocarbons.58  The  chlorination  of  petroleum  pentane  has 
become  of  industrial  importance  in  connection  with  the  manufacture 
of  synthetic  amyl  acetate  (see  page  89) .  In  order  to  produce  mainly 
monochlorides,  it  is  necessary  to  stop  the  chlorination  after  the  concen- 
tration of  monochlorides  in  the  reaction  mixture  has  reached  about  20 
per  cent,  and  separate  the  unchanged  pentane  by  fractional  distilla- 
tion. The  relative  proportions  of  the  isomeric  monochlorpentanes 
formed  are  not  known.  Cyclohexane  is  more  reactive  to  halogens  than 
n.hexane.  When  n.hexane  is  chlorinated,  the  CH2  groups,  not  the 
CH3  groups,  are  attacked59 

The  chlorination  of  paraffine  wax  is  carried  out  industrially,  the 
product  being  used  as  a  solvent  for  dichloramine  — T.60  Boiling  the 
product  with  aniline  readily  removes  most  of  the  chlorine.  The  higher 
boiling  petroleum  fractions,  are  readily  chlorinated  in  diffused  day- 
light at  ordinary  temperature,  but  the  products  are  very  unstable. 

Bromine  reacts  more  slowly  with  the  paraffines.  Pentanes  may  be 
brominated  readily  under  the  influence  of  intense  illumination,  and  the 
higher  paraffines  react  readily  with  bromine  when  gently  warmed  and 
illuminated.  In  the  presence  of  metallic  iron  or  ferric  bromide,  bro- 
mine readily  forms  a  series  of  substitution  products  in  which  one  bro- 
mine atom  is  attached  to  each  carbon  atom,  thus 

CH3CH2CH2CH2CH3 >  CH2Br .  CHBr .  CHBr .  CHBr .  CH2Br . 

Normal  heptane  and  an  excess  of  bromine  in  the  presence  of  iron 
yields  1,  2,  3,  4,  5,  6,  7-heptabromoheptane.  Ethyl  bromide  may  be 
brominated  under  these  conditions  to  ethylene  bromide  and  propyl 
bromide  to  1 . 2-dibromopropane.61  Bromides  have  been  made  by  treat- 
ing chlorine  derivatives,  such  as  CC14,  C2C14  and  C2C16,  with  anhydrous 
aluminum  bromide.62 

Sodium  iodide  reacts  with  many  alkyl  chlorides  and  bromides  to 

"Crossley  &  Renouf.  J.  Chem.  &oc.  91,  81  (1907). 

""Aschan,  Chem.  A~bs.  1919,  2868. 

59  Ber.  89,  2138  (1906);  Strauss  claims  to  be  able  to  prepare  primary  mono- 
chlorides  by  chlorinating  at  reduced  pressures  and  temperatures  above  the  boiling- 
point  of  the  hydrocarbons.  (German  Pat.  267,  204.) 

«°Dakin  &  Dunham.  Brit.  Med.  J.  1918,  I,  51. 

"V.  Meyer  &  Mtiller,  J.  prakt.  Chem.   (2)  J,6,  171   (1892). 

«2  Gustavson,  Chem.  Zentr.  18S1,  131,642. 


CHEMICAL  PROPERTIES  OF  SATURATED  HYDROCARBONS      65 

give  the  corresponding  alkyl  iodide  and  sodium  chloride  or  bromide. 
Sodium  iodide  dissolves  readily  in  acetone  and  this  solvent  yields  the 
best  results  in  carrying  out  the  reaction,  which  usually  takes  place  at 
once  at  ordinary  temperatures,  with  the  separation  of  sodium  chloride 
or  bromide.63 

Unsaturated  substances  may  be  brominated  without  affecting  the 
double  bond,  substitution  taking  place,  by  employing  N-bromo-aceta- 
mide.  Thus 

(CH3)2C  =  C(CH3)2  yields  (CH3)2C  =  C(CH3)  CH2Br. 

Sodium  hypobromite,  although  a  very  energetic  oxidizing  agent, 
converts  acetone  into  carbon  tetrabromide  (and  acetic  acid).  Bromo- 
form  also  yields  carbon  tetrabromide  with  this  reagent.64 

In  the  great  majority  of  cases,  it  is  much  preferable  to  prepare 
alkyl  halides  from  an  alcohol  or  olefine  than  by  treating  the  hydro- 
carbons themselves  with  chlorine  or  bromine,  the  latter  method  giving 
mixtures  of  isomeric  derivatives.  Since  it  is  usually  possible  to  ob- 
tain the  simpler  aliphatic  alcohols  in  a  state  of  purity,  they  constitute 
a  valuable  raw  material  for  the  preparation  of  pure  mono-halides. 
The  methods  employed  will  only  be  mentioned  and  reference  made  to 
original  articles  or  works  on  preparative  methods  for  further  data.65 

(1)  Hydrochloric  acid  gas,  and  methyl  or  ethyl  alcohol  in  the 
presence  of  zinc  chloride  gives  good  yields  of  the  corresponding  chlo- 
rides, but  this  method  is  practically  valueless  with  the  higher  alcohols 
on  account  of  the  instability  of  the  higher  alkyl  chlorides  in  the  pres- 
ence of  zinc  chloride.    Tars  or  heavy  polymers  are  formed  with  the 
higher  alcohols.    However,  Norris66  has  obtained  good  yields  from  a 
large  number  of  alcohols  by  using  a  large  excess  of  concentrated  hydro- 
chloric acid,  without  zinc  chloride. 

(2)  Hydrobromic  acid  and  hydriodic  acid  give  very  much  better 
yields,  than  hydrochloric  acid.    With  the  simpler  alcohols  the  well- 
known  sulfuric  acid  and  sodium  bromide  method  gives  excellent  re- 
sults, but  not  with  the  higher  alcohols.    In  the  case  of  the  higher  alco- 
hols much  better  results  are  obtained  by  the  method  of  Norris,66  in 
which  the  alcohol  is  gently  heated  with  the  concentrated  aqueous  acid 

«  Finkelstein,  Ber.  43,  1528   (1910). 

"Dehn,  J.  Am.  CJhem.  Soc.  SI,  1220   (1909). 

««Weyl,  Methoden  d.  Org.  Chem.  II.  1077. 

••Norris,  Watt  &  Thomas,  J.  Am.  Chem.  Soc.  38,  1071  (1916).  Norris  &  Mulliken : 
J.  Am.  Chem.  Soc.  48,  2093  (1920).  According  to  the  author's  experience,  the  halides 
prepared  according:  to  this  method  are  purer  and  much  preferable  to  similar  products 
made  by  other  methods.  Particularly  is  this  true  when  the  halides  are  to  be  employed 
in  a  Grignard  reaction.  According  to  German  Patent  280,740  the  addition  of  calcium 
chloride  is  advantageous. 


66        CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

and  the  alkyl  halide  removed  as  formed  by  distillation  from  the  mix- 
ture. This  method  gives  especially  good  yields  with  tertiary  amyl 
alcohol,  tertiary  butyl  alcohol,  octyl  alcohol,  cetyl  alcohol,  etc.  By 
the  Norris  method  good  yields  are  obtainable  in  many  cases  with  con- 
centrated hydrochloric  acid.  In  this  connection  it  is  of  interest  to  note 
that  the  glycol  S(CH2CH2OH)2  gives  the  dichloride  quantitatively 
with  concentrated  aqueous  hydrochloric  acid  at  60°. 67  Tertiary  alco- 
hols of  the  type  ROCH2C(OH)R2  give  excellent  yields  of  the  chloride 
on  warming  with  38%  hydrochloric  acid.68 

(3)  The  use  of  PC13,  PC15  and  PBr3  in  preparing  alkyl  chlorides 
and  bromides  is  well  known,  but  the  yields  are  greatly  reduced  by  the 
formation  of  esters  of  phosphorus  or  phosphoric  acid.    Iodides  are  com- 
monly made  by  introducing  iodine  into  a  mixture  of  the  alcohol  and 
red  phosphorus  which  method  has  been  recently  improved  for  the 
simpler  alkyl  iodides  by  Adams  and  Voorhees.69    Dehn  and  Davis70 
state  that  yields  of  85  and  88  per  cent  of  isobutyl  and  iso-amyl  chlo- 
rides respectively  can  be  obtained  from  the  corresponding  alcohols 
by  adding  PC13  to  a  mixture  of  the  alcohol  with  concentrated  aqueous 
zinc  chloride.     In  the  case  of  tertiary  alcohols,  acetyl  chloride  fre- 
quently reacts  abnormally,  giving  the  corresponding  chlorides  instead 
of  the  acetates,  for  example,  dime  thy  Ibutylcarbinol  thus  yields  the  cor- 
responding chloride. 

(4)  It  is  well  known  that  olefines  combine  with  halogen  acids  to 
form  alkyl  halides.    In  the  case  of  hydrocarbons,  generally  the  halo- 
gen will  combine  with  that  carbon  atom  of  the  olefine  group  which  has 
combined  with  it  the  least  number  of  hydrogen  atoms,  which  generali- 
zation is  known  as  Markownikow's  rule: 

CH3CHI .  CH3 

CH3 

>C  —  CH3 
CH3     | 
Br 

However,  small  quantities  of  the  isomeric  halides  are  sometimes 
formed.  Thus  propylene  yields  very  small  quantities  of  n.propyl 

OTH.  T.  Clarke,  J.  Chem.  Soc.  101,  1583  (1913).  Gomberg,  /.  Am.  Chem.  Soc.  41, 
1415  (1919).  This  chloride  is  the  now  well  known  "Mustard  Gas." 

MPaloma,  Ghent.  Abs.  1919,  2862. 

«/.  Am.  Chem.  Soc.  41,  789   (1919). 

70  J.  Am.  Ohem.  Soc.  29,  1328  (1907)  ;  When  PC1?  reacts  with  an  alcohol,  succes- 
sive formation  and  decomposition  of  the  whole  series  of  possible  alkyl  phosphites 
results,  and  the  series  of  reactions  may  be  arrested  by  choosing  the  experimental 
conditions  to  get  very  large  yields  of  P(OR)3,  P(OR)2.OH,  P(OR).(OH)2  or  P(OH)« 
and  3  RC1.  [Milobeudzki  and  Sachnowski,  J.  Chem.  Soc.  Alia.  1918,  I.  477.] 


CHEMICAL  PROPERTIES  OF  SATURATED  HYDROCARBON**       67 

iodide,71  and  isobutylene  yields,  with  a  solution  of  HBr  in  acetic  acid, 
about  93  per  cent  tertiary  butyl  bromide  and  7  per  cent  isobutyl  bro- 
mide.72 Acetic  acid  solutions  of  hydrogen  chloride  and  bromide  have 
given  particularly  good  results  in  the  terpene  and  sesquiterpene  series, 
where  crystalline  hydrochlorides  are  often  difficult  to  obtain.73 

The  ability  of  an  olefine  to  combine  with  halogen  acid  depends 
somewhat  upon  its  structure.  Thus  trimethylethylene 

CH, 

>C  =  CH.CH3  combines  readily  with  hydrogen  chloride,  but  the 
CH3 

isomeric  amylenes  do  not.  Advantage  of  this  fact  is  taken  in  one  of 
the  synthetic  rubber  processes,74  in  which  normal  pentane  is  chlorinated 
to  a  mixture  of  monochlorides.  The  monochlorides  are  converted  into 
amylenes  by  passing  over  quicklime  at  385°  to  400°  and  the  resulting 
amylene  vapors  are  passed  over  alumina  at  450°.  The  amylene  frac- 
tion boiling  from  34°  to  38°  contains  trimethylethylene,  which  is  re- 
moved by  combining  with  hydrogen  chloride  and  the  tertiary  amyl 
chloride,  boiling  point  84°  to  86°,  isolated  by  fractional  distillation. 

Unstable  carbon  ring  structures  are  often  ruptured  by  halogen 
acids.  Pinene  in  acetic  acid  solution  gives  mainly  dipentene  dihydro- 
chloride,  with  rupture  of  the  bridged  or  cyclobutane  ring. 

Bromocyclopropane 75  and  bromocyclobutane 76  and  cyclopropyl 
carboxylic  acid  are  converted  into  open  chain  compounds  by  concen- 
trated hydrobromic  acid.  Thus 

CH2 

>CHBr  +  HBr >  CH3CHBr.CH3Br. 

CH2 


CH2 

>  CH .  C02H  +  HBr >  CH2Br .  CH2CH,CO2H 

H2 

Br:H 


vs 

j, 


CH2 :-CH2  CH2Br    CH3 

CH2 -CHBr  *  CH9 CHBr 


L2 

"Michael  &  Leighton,  J.  prakt.  Chem.  60,  348,  446   (1899). 

72  Ipatiev  &   Ogonowsky,   Ber.   86,   1988    (1903). 

73  For    good    results,    the    reaction    mixture    saturated    with    HC1    or    HBr    should 
be  allowed  to  stand  two  or  three  days  in  a  cool,  dark  place. 

7*Badische  A.  &  S.  Fab.  Brit.  Pat.  18,  356   (1911). 
"  Willstatter  &  Bruce,  Ber.  40,  4457   (1907). 
"Perkin,  J.  Chem.  Soc.  65,  950  (1894). 


68        CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

It  will  be  noted  in  the  last  case  that  the  bromine  atom  of  the  HBr 
molecule  combines  in  such  a  way  as  to  place  it  in  the  position  farthest 
removed  from  the  bromine  atom  already  present  in  the  ring.  This  il- 
lustrates the  positive-negative  rule  of  Michael,77  which  is  not  as  em- 
pirical as  Markownikow's  rule.  According  to  Michael's  principle  the 
combination  of  two  molecules,  for  example,  halogen  acid  and  an  olefine, 
tends  to  occur  with  such  structural  results  as  will  give  the  maximum 
degree  of  entropy,  that  is  the  neutralization  of  the  chemical  energies 
or  affinities  of  the  reacting  atoms.  This  generalization  is,  therefore,  a 
special  case  of  Ostwald's  hypothesis  that  "every  system  tends  towards 
that  state  whereby  the  maximum  entropy  is  reached.78 

Michael  formulated  his  principle  after  a  comprehensive  study  of 
addition  reactions.  The  marked  influence  of  a  methyl  group  is  shown 
in  the  formation  of  CH3CHBr.CH3  from  propylene,  CH3CBr2CH3 
from  CH3CBr=:CH2,  CH2Br.CH2.C02H  the  chief  product  of  HBr 
and  CH2  =<^H.C02H,  etc.  The  rule  is  not  without  many  exceptions, 
however.  Faworsky  79  considers  the  matter  from  the  standpoint  of 
relative  reaction  velocities.  By  heating  isopropyl  bromide  to  250°  sev- 
eral times,  removing  the  fraction  boiling  at  69°-70°  each  time  he  was 
able  to  effect  20  per  cent  conversion  of  isopropyl  bromide  to  normal 
propyl  bromide.  The  conversion  of  normal  propyl  bromide  to  iso- 
propyl bromide  is  therefore  reversible  and  the  addition  of  HBr  to 
propylene  takes  place  in  part  contrary  to  Markownikow's  rule  and 
Michael's  principle,  the  result  being  dependent  upon  the  relative  ve- 
locities of  the  two  reactions. 

(1)  CH3CH  =  CH2  +  HBr »  CH3CHBr.CH3   (main  result) . 

(2)  CH3CH  =  CH2  +  HBr >  CH3CH2CH2Br 

Similar  reversible  relations  were  found  in  the  bromopentane  series. 
Faworsky  confirmed  the  earlier  observation  of  Eltekow  that  isobutyl 
and  tertiary  butyl  bromides  are  in  equilibrium  at  about  210°,  as  noted 
in  the  following: 

CH3  CH3 

(CH3)3CBr^HBr+        >C  =  CH2?±         >CHCH2Br. 
CH3  CH3 

In  a  similar  manner  it  was  shown  that  ethylidene  bromide  is  present 
in  the  mixture  resulting  from  heating  ethylene  bromide: 

"J.  prakt.  Chem.  1,6,  205    (1892). 

78 J.   prakt.   Chem.   60,  286,    292    (1899);    Bcr.   39,   2138    (1906). 

"Ann.  354,  325    (1907). 


CHEMICAL  PROPERTIES  OF1  SATURATED  HYDROCARBONS      69 

CH2Br        CHBr 

±5  1 1          +  HBr<p±CH3CHBr2 
CH2Br        CH2 

Hydrogen  bromide  combines  with  CH2  =  CH .  CH2Br  in  the  light  to 
form  trimethylene  bromide,  CH2Br.CH2CH2Br  quantitatively,  but  in 
the  dark  considerable  propylene  bromide  is  formed.80 

General  Properties  of  the  Simpler  Alkyl  Halides:  One  of  the  most 
conspicuous  properties  of  the  alkyl  halides  is  the  relative  ease  with 
which  they  are  decomposed  by  heat  to  form  olefines  and  halogen  acid. 
Accurate  data  are  practically  confined  to  the  simpler  substances.  The 
decomposition  of  the  two  propyl  bromides  was  studied  by  Aronstein.81 

PER  CENT  DISSOCIATION  BY  HEAT. 

Temperature  n. Propyl  Bromide                            Isopropylbromide 

113°  ....  5.40 

138°  ....  7.30 

180°  2.9  15.10 

210°  10.4  21.00 

262°  31.9  56.00 

Roozeboom  82  has  determined  similar  values  for  the  decomposition  of 
tertiary  butyl  bromide  to  isobutylene  and  HBr.83 

Temperature  Per  Cent  Dissociation 

115°  42 

130°  10.0 

150°  26.0 

183°  42.6 

204°  60.0 

250°  76.0 

300°  85.2 

Chlorine  and  bromine  derivatives  of  petroleum  fractions,  kerosene 
fractions  for  example,  are  very  unstable,  and  as,  noted  by  Markowni- 
kow  84  and  others,  decompose  slowly  at  ordinary  temperatures  with 
liberation  of  halogen  acid.  When  such  chlorine  or  bromine  deriva- 
tives are  treated  with  sodium  iodide  in  acetone  free  iodine  is  liberated. 
The  decomposition  of  these  halides  is  probably  accelerated  by  light.85 
Kipping  and  Davies  attribute  the  instability  of  chlorinated  petroleum 
oils  to  compounds  of  the  type  R3CX. 

The  dissociation  of  alkyl  halides,  particularly  in  the  presence  of 

80  Holleman  &  Matthes,  Chem.  Als.  1918,  2545. 

81  Rec.  trav.  chim.  1,  134  (1882). 
KBer.  14,  2396   (1881). 

83  The  decomposition  of  amyl  bromides  by  heat  has  recently  been  investigated 
by  Colson.  Compt.  rend.  1918,.  1548. 

"Awn.   301,   185    (1898). 

86Pfeiffer,  Z.  angew.  Chem.  1913,  545,  noted  the  decomposition  of  nitro  stilbene 
dichloride  by  light. 


70        CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

aluminum  chloride,  is  intimately  associated  with  the  subject  of  the  re- 
arrangements which  alkyl  halides  and  defines  undergo.  Thus  Freund 86 
showed  that  isobutyl  halides  were  partially  converted  into  tertiary 
derivatives  on  heating  with  aluminum  chloride  in  sealed  tubes,87  and 
the  formation  of  tertiary  butyl  derivatives  of  benzol  toluene  and  xylene 
by  condensing  isobutyl  chloride  or  bromide  with  these  hydrocarbons 
according  to  Friedel  and  Crafts'  method  has  been  well  established  by 
Baur.88  Nef  has  advanced  two  explanations  of  such  rearrangements. 
In  his  earlier  work  he  supposed  the  intermediate  formation  of  a  nas- 
cent olefine.  According  to  this  theory  the  formation  of  tertiary  butyl 
ethyl  ether  from  isobutyl  iodide  and  alcoholic  silver  nitrate  is  as  fol- 
lows: 

CH3  CH3 

(a)  >  CHCH2Br >         >  C  —  CH2 

CH3  CH8      |        | 

CH3  CH3 

(b)  >  C  —  CH2  +  C2H5OH >        >  C  —  CH3 

CH3      ||  CH3      | 

OC2H5 

In  a  similar  manner  isobutyl  iodide  and  silver  cyanate  yield  a  mixture 
of  about  two  parts  tertiary  butyl  isocyanate  and  one  part  of  the  iso- 
butyl derivative;  silver  acetate  in  acetic  acid  yields  about  two  parts 
tertiary  butyl  acetate  to  one  part  isobutyl  acetate.89  Wischnegradsky 
showed  that  secondary  iso-amyl  alcohol  with  halogen  acids  yields 
chiefly  the  tertiary  halide.90 

CH3 

>CHCH.CH3  CH3 

CH3  I  — >         >C.CH2CH9 

6H  CH3      | 

Also  the  secondary  halide,  when  heated  with  lead  hydroxide,  yields  the 
tertiary  alcohol. 

But  the  facts  are  somewhat  more  involved  than  is  indicated  above. 
Thus  isobutyl  alcohol,  when  decomposed  by  heat,  and  the  primary 
isobutyl  halides  with  alcoholic  alkali  gives  a  mixture  of  butylenes 

88  J.  prakt.  chem.  (2),  12,  26  (1875). 

87  The  nature  of  the  decomposition  products  of  alkyl  halides  in  the  presence  of 
anhydrous  aluminum  chloride,  either  alone  or  in  the  presence  of  saturated  or  un- 
saturated  non-benzenoid  hydrocarbons,  has  never  been  carefully  investigated.  Cf.  Meyer, 
Ber.  27,  2766  (1894). 

88Ber.  24,  2832  (1891)  ;  31,  1344  (1898)  ;  32,  3647  (1899).  Nitrated  tertiary  butyl- 
toluene  and  xylene  are  known  commercially  under  the  name  of  artificial  musk. 

88Butlerow,   Ann.  168,   143    (1873);    Nef,   Ann.   309,150    (1899). 

90  Ann.  190,  342   (1878). 


CHEMICAL  PROPERTIES  OF  SATURATED  HYDROCARBONS      71 

which  have  been  shown  to  contain  isobutylene  and  a  and  (3-normal 
butylenes. 

CH3  CH3 

>  CH  .  CH2X  -  >         >  C  =  CH2  and 

CH3  CH3 


and 
CH3CH2CH  =  CH2 

Nef  believed  that  such  facts  could  best  be  explained  by  the  inter- 
mediate formation  of  a  cyclopropane  ring,  which  structure  is  known 
to  be  ruptured  easily.  Thus 

CH3  -  CH  -  CH2X      CH3  -  CH  -  CH  < 

CH2H  CH2H 

CH3  -  CH  -  CH2      CH3  -  CH  -  CH2  -  CH2     CH3CH  =  CHCH3 
CH2  ^CH3CH2CH  =  CH2 


CH3  CH3 

(a)  >CHCH2Br  -  »         >C  —  CH2 
CH3  CH3      |        | 

CH3  CH3 

(b)  >C  —  CH2  +  C2H5OH  --  >         >C  —  CH3 


The  reaction  of  the  solvent  is  frequently  important  in  such  reactions. 
Isobutyl  iodide  and  silver  acetate  give  a  small  yield  of  about  equal 
parts  of  isobutyl  acetate  and  tertiary  butyl  acetate.  Tertiary  butyl 
iodide,  however,  does  not  give  the  acetate  except  when  acetic  acid  is 
employed  as  a  solvent.  It  is  significant  also  that  tertiary  butyl  iodide 
gives  only  isobutylene  when  treated  with  silver  cyanide,  oxide  or 
cyanate,  nothing  resembling  a  so-called  double  decomposition  reaction 
taking  place.  Tertiary  butyl  iodide  and  silver  nitrate  in  alcohol 
solution  gives  no  trace  of  tertiary  butyl  nitrate;  nitric  acid  is  not 
known  to  react  with  a  double  bond  to  give  an  alkyl  nitrate,  in  the 
same  manner  that  sulfuric  acid  yields  alkyl  sulfuric  esters.92 

92  Nef,  loc.  cit. 


72        CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

In  the  amylene  series  several  cases  of  rearrangement  have  been 
well  established  which  are  capable  of  a  similar  explanation.  Thus 
primary  iso-amyl  alcohol  and  the  corresponding  halides  yield  chiefly 
trimethyl  ethylene; 

CH3  CH3  / 

>CHCH2CH/ 
CH3 


>CH.CH2CH2X 


CH3 

CH3 

>C  — CH2 
CH8       \/ 
CH2 


CH3 
CH 


>C  —  CH2  —  CH 


CH3 
CH3 


=  CH.CH3 


The  formation  of  this  olefine  from  bromotetramethylmethane,  ob- 
served by  Tissier 93  may  be  similarly  explained  without  resorting  to 
the  vague  idea  of  the  "wandering"  of  the  methyl  group. 

->(CH3)2C-CH2 


(CH3)  2C  —  CH2Br  -»  (CH3)  2C  — 

CH9-H  CH,   H 


>  (CH3) 2C  —  CH2  —  CH2  -*  (CH,) 2C  =  CH .  CH3 

Another  rearrangement  involving  a  change  in  the  position  of  a 
methyl  group  is  that  noted  by  Coutourier.94 

CH3 

>  C  —  CHBr  —  CH3  CH3 

CH3     1  »         >C_-C-CH3 

2H  CH3 


CH3 

>C  — CH.CH3 
CH3      |/ 
CH, 


CH3 
CH3 


CH3 
CH3 


Some  support  for  Nef's  theory  of  such  changes  is  found  in  the 
properties  of  the  cyclopropane  ring  (see  page  77) . 

The  mechanism  of  dissociation  of  the  alkyl  halides  and  their  so- 


•*Ann.  chim.  phys.   (6),  29,  361   (1893). 
"Ann.  chim.  phya.  (6),  26,  464   (1892). 


CHEMICAL  PROPERTIES  OF  SATURATED  HYDROCARBONS      73 

called  double  decomposition  reactions  is  of  fundamental  importance. 
Nef 95  has  advanced  the  theory,  which  he  has  developed  from  his 
previous  studies  of  bivalent  carbon,  that  alkylidene  dissociation  first 
occurs. 

(a)  RCH2CH2X >  RCH2CH<  +  HX 

(b)  RCH2CH<          -^RCH  =  CH2 

Whether  or  not  olefmes  are  found  in  the  reaction  products  de- 
pends upon  the  presence  or  absence  of  substances  capable  of  reacting 
with  the  very  reactive  alkylidene,  the  rate  of  this  reaction  as  com- 
pared with  the  rate  of  the  rearrangement  to  the  olefine,  and  other 
secondary  factors.     Thus  Nef  explains  the  apparently  contradictory 
results  obtained  by  previous  investigators  by  showing  that  when  ethyl 
;  chloride  is  decomposed  by  heating  to  550°  and  the  gases  subsequently 
passed  over  soda  lime  to  remove  the  hydrogen  chloride,  a  nearly  quan- 
titative yield  of  ethylene  was  obtained.    If,  however,  ethyl  chloride 
is  passed  directly  into  hot  soda  lime  at  550°  ethyl  alcohol  or  rather 
I  the  decomposition  products  of  ethyl  alcohol  under  these  conditions, 
I  acetate,  carbonates,  methane  and  hydrogen,  are  obtained.    Hydrogen 
chloride  acting  upon  the  soda-lime  liberates  water,  which  may  then 
react  with  the  labile,  reactive  alkylidene  as  follows: 

(a)  CH3CH<  +  HOH 

(b)  CH3CH<  +  H20 

The  behavior  of  the  simpler  alkyl  halides  to  alcoholic  alkali  has 
been  thoroughly  investigated  by  Nef,  with  the  results  summarized  be- 
low: 

Halide                    Olefine  %  Ether  %           Temp.  °C. 

C.HsBr  11.  60.  -70.  70  ±  5 

C2H5I  14.  60.  40-  90 

CH3CH2CH2Br  20.  60.  80-100 

CH3CH2CH2I  36.4  40.  80-100 

CH3CHBr.CH3  75.0  17.  80-100 

CH3CHI.C3H  93.6  0.?  80-100 

(CH3)2CHCH2C1  ....  37.                           120      (Sodium 

"  38  5                         170      I  isobutylate  used 

(CH3)2CHCH2Br  64.  23.  90-100 

(CHa)2CHCHJ  98.  0.  90-100 

CH, 

(CH3)2C<  97.  0.  90-100 

a 

"Ann.  309,  128  (1899)  ;  SIS,  3  (1901). 


74        CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

Halide  Olefine  %         Ether  %  Temp.°C. 

CH3 
(CH3)2C<  97.  0.  90-100 

I 

(CH8)2CH.CH2CH2Br  ....  70.5  90-100 

(CH3)2CH.CH2CH2I  ....  51.  90-100 

C2H8 
(CH3)2C  <  80.  ?  50-  60 

Br 
CHJ3r.CHj.Br  — >  vinyl  bromide,  quantitative. 

Vaubel 96  has  shown  that  allyl  halides  give  chiefly  allyl  ether  with 
alcoholic  alkali  under  a  wide  variety  of  conditions.  (For  the  influ- 
ence of  double  bonds  upon  the  reactivity  of  adjacent  halogen  atoms  see 
page  000.)  Nef97  has  also  shown  that  the  alkyl  sulfates,  ethyl,  n .  propyl, 
isobutyl  and  iso-amyl,  react  with  alcoholic  caustic  potash  to  give 
mainly  the  ethers  ROC2H5.  On  heating  the  alkyl  halides  with  water, 
alcohols  and  olefines  are  formed.  The  employment  of  high  pressures 
during  the  hydrolysis  greatly  increases  the  yield  of  alcohols  from 
chloropentanes.98 

Acetates  are  formed  when  the  alkyl  halides  are  heated  with  an  ace- 
tate of  sodium,  potassium,  silver  or  lead  and  the  best  results  appear  to 
be  obtained  in  glacial  acetic  acid  under  pressure.  As  with  ether  for-; 
mation  noted  by  Nef  the  best  yields  of  alkyl  acetates  are  obtained 
from  the  alkyl  chlorides,  iodides  giving  the  poorest  yields.  This  well- 
known  method  is  of  general  application.  It  is  applied  industrially  in 
the  manufacture  of  artificial  amyl  acetate  and  also  in  the  terpene  series 
in  the  conversion  of  bornyl  chloride  into  the  acetates  of  borneol  and 
isoborneol.99 

The  alkyl  halides  and  metallic  nitrates  give  very  small  yields  of 
alkyl  nitrates.  Thus  Bertrand,100  with  methyl,  ethyl  and  propyl 
iodides  and  silver  nitrate  obtained  free  nitric  acid,  and  small  quantities 
of  ethers  and  alkyl  nitrates.  Tertiary  butyl  iodide  and  alcoholic  silver 
nitrate  yield  isobutylene  and  tertiary  butyl  ethyl  ether  in  about  equal 
amounts.101  Ethylene  bromide  and  alcoholic  silver  nitrate  gives  a 
trace  only  of  the  dinitrate,  a  little  free  nitric  acid,  some  glycoldiethyl 
ether  and  the  chief  reaction  product  is  the  ethyl  ether  mononitrate 

CH2OC2H5 

H2ON02 

*Ber.  24,  1685  (1891). 

"  Ann.  SIS,  3   (1901).  t  +  M*^ 

"Essex,  Hibbert  &  Brooks,  J.  Am.  Uhem.  Soc.  38,  1369   (1916). 

99  Camphene  is  the  principal  reaction  product. 

™Bull.   Soc.   Chim.   S3,  566    (1881). 

""Nef,  Ann.  S09,  150  (1899). 


CHEMICAL  PROPERTIES  OF  SATURATED  HYDROCARBONS      75 

Alkyl  halides,  particularly  chlorides,  can  be  converted  into  the  cor- 
responding alcohols  by  heating  with  alkali  formate  in  methyl  alcohol 
solution.  Henry  102  first  noted  the  ease  with  which  certain  alkyl  for- 
mates react  with  methyl  alcohol  to  give  methyl  formate  and  an  alcohol. 
Nef  prepared  acetol  in  this  manner  and  excellent  yields  of  ethylene- 
glycol  can  be  obtained  from  ethylene  chloride.103 

(1)  RCH2Cl  +  Na02CH-     ->RCH202CH  (alkyl  formate) 

(2)  RCH202CH  +  CH3OH  -     ->  RCH2OH  +  CH3O2CH  +  NaCl 

There  is  no  appreciable  difference  in  the  behavior  of  alkyl  and  non- 
benzenoid  cyclic  halides  toward  magnesium  and  in  the  various  appli- 
cations of  the  Grignard  reaction.  To  cite  a  few  examples  among  many, 
Borsche  used  the  Grignard  synthesis  of  sulfinic  acids  to  convert  cyclo- 
pentyl  bromide  into  cyclopentanesulfinic  acid,104  and  Bouveault  used 
bromocyclohexane  in  the  preparation  of  cyclohexanol.105  Hesse  has 
patented  the  conversion  of  bornyl  chloride  to  borneol  by  the  use  of  the 
Grignard  reaction,106  but  in  this  case,  as  with  the  higher  alkyl  halides, 
the  yields  are  very  poor.  Bromocyclohexane,  like  normal  and  iso- 
hexane  monobromides,  is  unstable.  Alcoholic  caustic  potash  yields 
mainly  cyclohexene. 

102  Bull.  acad.  roy.  *elg.  1902,  445. 

108  Brooks  &  Humphrey,  J,  Ind.  &  Eng.  CJtem.  9,  750   (1917). 

104  Ber.  40,  2220  (1907). 

106  Bull.  soc.  cMm.    (3),  29,  1049    (1903). 

106  U.   S.  Pat.  826,165;   826,166. 


Chapter  III.     The  Paraffine 
Hydrocarbons. 

Methane. 

Methane  is  described  in  a  special  section  on  account  of  its  com- 
mercial importance.  One  liter  of  methane  (made  by  the  action  of 
water  on  magnesium-methyl  iodide)  weighs  0.7168  grams  at  0°  and 
760  mm.  pressure.1  Its  melting-point  is  —  184°.  2  Its  boiling-point 
under  760  mm.  pressure  is  —  164°.  3  The  critical  temperature  is 
—  82.85°,  the  critical  pressure  45.60  atmospheres,  and  the  critical  den- 
sity 0.1623.4  The  coefficients  of  expansion  x  106  are  A  =  3687  and 
B  =  3681.  5 

The  liquefaction  of  methane  has  recently  become  of  industrial  im- 
portance in  connection  with  the  separation  of  helium  from  natural  gas. 
Pure  methane  may  be  separated  from  ethane  and  other  hydrocarbons 
in  this  manner,  which  is  a  matter  of  some  importance  in  the  industrial 
chlorination  of  methane.  Although  both  the  Linde  and  Claude  proc- 
esses have  been  employed  on  a  large  scale  for  this  purpose,  little  tech- 
nical information  has  been  published.  Satterly  and  Patterson  6  have 
determined  the  latent  heat  of  vaporization  of  methane  to  be  130  calories 
per  gram  and  ethane  260  calories  per  gram.  Satterly  7  has  shown  that 
nitrogen  dissolves  in  liquid  methane  at  moderate  pressures  and  Mc- 
Taggart  and  Edwards  8  have  determined  the  temperature  and  compo- 
sition relations  in  the  liquid  and  gas  phases  in  the  system  methane- 
nitrogen. 

The  flame  of  methane  is  not  very  luminous.  When  burned  in  an 
Argand  burner  at  the  rate  of  one  cubic  foot  per  hour  it  gives  a  flame 
of  5.2  candle  power.  Pure  methane  on  combustion  yields  1003  B.T.U. 

1Guye,  Chem.  Zentr.  1909  I.  977. 

4  Baume  &  Perrot,  compt.  rend.  148,  39  (1909)  ;  also  Wahl,  Proc.  Roy.  Soc.  87A,  371. 

•Moisaan  &  Chavanne,  Compt.  rend.  Itf,  407    (1905)  ;  Olszewski,  Compt.  rend.  100, 


'Cardoso,  Arch.  aci.  phya.  nat.  36,  97,  39,  400. 
•Leduc,  Compt.  rend.  148,  173   (1909). 
•Trans.  Roy.  Soc.  Canada.  13.  123  (1919). 
7  Ibid.,  IS,  109   (1919). 
•Ibid.,  IS,  67  (1919). 

76 


THE  PARAFFINS  HYDROCARBONS  77 

per  cubic  foot.9  Values  for  natural  gas  vary  from  950  to  about  1250 
B.T.U.  per  cubic  foot. 

Methane  has  no  physiological  effect  on  men  or  animals  except  when 
present  in  sufficient  per  cent  to  produce  the  characteristic  symptoms 
of  oxygen  deficiency.  Mine  gas  and  other  mixtures  of  methane  and  air 
may,  therefore,  contain  sufficient  methane  to  form  explosive  mixtures 
and  yet  cause  no  physiological  symptoms  which  might  serve  as  a  warn- 
ing to  miners.  Haber 10  has  developed  an  interesting  automatic  warn- 
ing whistle. 

'The  largest  explosive  limits  for  methane  and  air  are  those  deter- 
mined by  Burrell  and  Oberfell,  i.  e.,  a  minimum  methane  content  of 
4.9  per  cent  and  a  maximum  of  15  to  15.4  per  cent.11  Initial  pressures 
of  5  atmospheres  do  not  appreciably  effect  these  ratios,  so  that  these 
values  are  practically  independent  of  ordinary  variations  of  barometric 
pressure.  Burgess  and  Wheeler,12  and  Wheeler  13  find  somewhat  nar- 
rower limits.14  Wheeler15  also  finds  that  moderate  changes  of  pres- 
sure have  only  very  slight  effects  on  the  explosion  limits.  Coward, 
Carpenter  and  Pay  man,16  give  5.6  per  cent  methane  as  the  lower  limit 
of  explosibility.  Methane  and  oxygen  ignite  at  667°  and  although  this 
ignition  point  is  somewhat  lowered  by  certain  metals,  oxidation  in  the 
presence  of  palladium  is  not  appreciable  below  404°. 17  This  fact 
makes  possible  the  quantitative  determination  of  hydrogen  in  the  pres- 
ence of  methane  by  selective  combustion.18 

•  Richards,  "Metallurgical  Calculations,"  1918,  p.  25,  gives  970  B.  T.  U.  per  cubic 
foot  as  the  net  heat  of  combustion  of  methane:  ethane  1719  B.  T.  U.  and  propane 
2464  B.  T.  U.  per  cubic  foot. 

10  (The  U.  S.  Bureau  of  Mines  has  recently  demonstrated  a  highly  efficient  system 
of  warning  miners  of  danger  by  introducing  butyl  mercaptan  in  the  air  supply.)      The 
Haber   apparatus   for   the   detection   of  methane   in   mine  gases  gives   warning   as   the 
percentage  of  methane  approaches  the  limit  of  explosibility.     It  is  based  on  the  principle 
that   differences   in    the   density    of   a   gas   are  indicated   by    differences   in   the   sound 
produced    by    blowing    a    whistle    or    pipe    with    the    gas.      The    apparatus    contains 
two   stopped   pipes,    which    are   tuned   to   the    same    pitch    when   filled   with    the   same 
gas.       When    one    whistle    is    supplied,    by    piped    connections,    with    a    mixture    of 
methane  and  air  in   the  proportions   corresponding   to  the  lower  explosive  limit,   and 
the    other    supplied    with    the    mine   air,    then    the    simultaneous    blowing    of    the    two 
whistles   produces   a   beat   whose   interval    diminishes   as   the    pitch    of   the   two    pipes 
approach   the  same  value,   or  as  the  mine  gas   approaches  the   dangerous  composition 
gas  in  methane  content.     When  near  the  explosion  limit  the  beat  produces  a  charac- 
teristic shrill  sound.     Cf.  Chem.  Ztg.  57,  1329   (1913). 

11  U.  S.  Bureau  of  Mines.  Techn.  Paper  119  and  121  (1916). 

12  J.  Chem.  Soc.  105,  2591    (1914). 

13  J.  Chem.  Soc.  105,  2606   (1914)  ;  also  Mason  &  Wheeler,  J.  Chem.  Soc.  113,  45 
( 1918) . 

14  Mixtures   of  methane   and   air   containing  9.6   per   cent   methane  are   the  most 
flammable,  and  the  rate  of  flame  travel  and  explosion  violence  is  greatest  with  mixtures 
of   this   composition.      Methane   and    oxygen,   in    molecular   proportions,   gives   a    flame 
velocity  of  7,616  feet  per  second.     Mason  &  Wheeler   [J.  Chem.  Soc.  117,  1227   (1920)1 
give  5.4  per  cent  as  the  lower  limit  of  methane  and  air  mixtures  for  horizontal  flame 
propagation. 

16  J.  Chem.  Soc.  Ill,  411    (1917). 
18  J.  Chem.  Soc.  115,  28   (1919). 

"Denham,  J.  Soc.  Chem.  Ind.  24,  1202  (1905);  Phillips,  Am.  Chem.  J.  16,  163 
(1894) . 

"Hempel,  Z.  anal.  Chem.  SI,  445    (1902);   Richardt,    Chem.  Zentr.  1904,  II.   364. 


78        CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

The  mechanism  of  the  combustion  of  methane  and  other  hydro- 
carbons has  been  studied  by  Bone  and  Wheeler 19  who  found  that 
formaldehyde  is  an  intermediate  product.  Formaldehyde  is  then  fur- 
ther oxidized,  with  the  possible  intermediate  production  of  formic  acid, 
to  water  and  carbon  dioxide.  They  represent  the  combustion  of  me- 
thane as  passing  through  the  stages  indicated  in  the  following: 

CD 

(2) 


(3) 

(4)        2CO  +  02 »2C02 

Methane  is  exceptionally  stable  to  heat.  Bone  and  Coward  20  have 
shown  that  its  decomposition  at  700°  is  not  appreciable,  but  at  slightly 
higher  temperatures  it  is  decomposed  directly  into  carbon  and  hydro- 
gen without  the  formation  of  ethylene  or  acetylene.  Coward  and  Wil- 
son 21  showed  that  at  850°  the  equilibrium  mixture  contains  97.5  per 
cent  hydrogen  and  2.5  per  cent  methane.  At  1000°  the  equilibrium 
mixture  consists  of  1.1  per  cent  methane  and  98.9  per  cent  hydrogen. 
At  1200°  Pring  and  Fairlie  22  found  a  gas  mixture  in  equilibrium  with 
amorphous  carbon  containing  0.36  per  cent  methane.  The  carbon 
formed  by  decomposing  methane  in  hot  tubes,  hot  furnace  checker  work 
and  the  like  is  not  a  good  commercial  black  but  is  gray-black  in  color 
and  usually  gritty.  Whitaker  and  Alexander  23  have  called  attention 
to  the  fact  that  in  gas  mixtures  produced  by  the  thermal  decomposition 
of  hydrocarbons,  equilibrium  corresponding  to  the  temperature  em- 
ployed is  rarely,  if  ever,  attained.  The  composition  of  the  gas  is  not 
only  dependent  upon  the  temperature  to  which  the  mixture  is  sub- 
jected, but  is  also  markedly  affected  by  the  time  of  heating,  the  pres- 
sure and  the  presence  or  absence  of  substances  which  may  catalytically 
influence  the  tendency  to  establish  equilibrium. 

When  methane  is  decomposed  in  contact  with  metals,  metallic  car- 
bides are  sometimes  formed;  in  fact,  it  has  been  proposed  to  intro- 

»J.  Chem.  8oc.  81,  541  (1902)  ;  83,  1074  (1903)  ;  Cf.  Armstrong,  J.  Chem.  Soc. 
83,  1088  (1903). 

20  J.   Chem.  Roc.  93,  1197    (1908). 

ai  J.  Chem.  Soc.  115,  1380   (1919). 

**J.  Chem.  Soc.  101,  91  (1911)  ;  Bone  &  Jordan,  J.  Chem.  Soc.  11,  41  (1897)  :  79, 
1042  (1901). 

u  J.  Ind.  d  Eng.  Chem.  6,  383  (1914). 


THE  PARAFFINS  HYDROCARBONS  79 

duce  carbon  into  molten  iron  in  this  manner.  Magnesium  carbide  is 
rapidly  formed  by  heating  the  metal  with  methane  at  760°.  Man- 
ganese also  readily  forms  a  carbide  when  heated  to  800°  in  methane.24 

Chlorination  of  Methane:  The  industrial  production  of  carbon 
tetrachloride,  methyl  chloride,  chloroform  and  dichloromethane  from 
methane  or  natural  gas,  is  peculiarly  an  American  opportunity  on  ac- 
count of  the  availability  of  natural  gas.  No  process  for  the  manu- 
facture of  methane,  as  by  the  hydrogenation  of  carbon  monoxide,  has 
as  yet  been  operated  on  an  industrial  scale.  The  problem  of  manufac- 
turing these  chlorinated  derivatives  is  an  old  one  but  recent  interest  in 
this  direction  is  coincident  with  the  steadily  increasing  value  of  the 
products  of  wood  distillation,  particularly  methyl  alcohol  and  acetone, 
and  the  rapid  development  of  the  electrolytic  chlorine  industry  and 
relatively  cheap  liquid  chlorine.  Obviously,  the  maximum  economic 
advantage  would  be  secured  by  bringing  natural  gas  and  electrolytic 
chlorine  production  together.  As  pointed  out  elsewhere,  natural  gas 
varies  considerably  in  the  proportions  of  methane  and  other  hydrocar- 
bons, but  so-called  dry  gases  containing  very  low  percentages  of  ethane 
and  higher  methane  homologues  are  widely  distributed.  According 
to  reported  analyses  25  such  dry  gas  is  available  at  numerous  locali- 
ties in  the  Louisiana,  Texas  and  California  fields  and,  as  has  already 
been  pointed  out,  pure  methane  can  be  separated  from  its  homologues 
by  liquefaction  methods  so  that  West  Virginia  or  other  gas  could  thus 
be  employed. 

Chlorine  and  methane  do  not  react  in  the  dark  at  ordinary  tem- 
peratures but  Bedford  26  states  that  fairly  good  yields  of  methyl  chlo- 
ride and  carbon  tetrachloride  may  be  obtained,  without  explosions, 
by  chlorinating  at  0°  in  strongly  actinic  light.  Baskerville  and  Ried- 
erer  27  state  that  ultraviolet  light  has  very  little  effect  upon  the  re- 
action but  that  intense  illumination  by  light  strong  in  the  visible  blue 
rays  is  much  more  effective.  Philips28  heated  the  chlorine-methane 
mixture  and  prevented  explosions  by  packing  the  heated  zone  with 
sand,  asbestos  or  bone  black,29  very  similar  to  the  method  of  smoothly 
chlorinating  acetylene.  At  300°  to  400°,  in  the  dark,  the  principal 
products  are  methyl  chloride  and  carbon  tetrachloride.  Tolloczko 

"Hilpert  &  Paunescu,  Ber.  46,  3479   (1913). 

26  Cf.  U.  S.  Bur.  Mines.  Techn.  Paper  #255,-ll,   (1921).  "Chlorination  of  Natural 
Gas"  by  Jones,  Allison  &  Meighan. 

28  J.  2nd.  &  Eng.  Chem.  8,  1090   (1916). 

27  J.  Ind.  &  Eng.  Chem.  5,  5   (1913). 

28  Aw.  Chem.  J.  16,  361    (1894). 

29  Yoneyama  &  Ban  [J.  Chem.  Soc.  Aba.  1321,  I.  3]  use  bone  black  and  fine  calcium 
oxide  at  250°. 


80        CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

and  Kling  30  obtained  a  yield  of  78  per  cent  carbon  tetrachloride  by 
'chlorinating  at  400°  in  contact  with  pumice,  and  impregnation  of  the 
pumice  with  cupric  chloride  is  said  to  favor  smooth  chlorination.  Chlo- 
rination  at  400°  is  also  described  by  Mackaye.31  The  effect  of  cat- 
alysts upon  these  reactions  is  of  interest,  particularly  as  regards  in- 
creasing the  yield  of  partially  chlorinated  products.  Passing  a  mix- 
ture of  the  two  gases  through  active  charcoal  at  90°  was  proposed 
by  Mallet  32  in  1879  and  Damoiseau  33  states  that  methyl  chloride  may 
be  chlorinated  mainly  to  chloroform  by  passing  the  proper  gas  mix- 
ture through  animal  charcoal  heated  to  250°-350°.  Garner  and  Clay- 
ton 3*  have  recently  patented  a  similar  method,  employing  a  specially 
activated  charcoal  as  the  catalyst.  Recent  experiments  of  Jones,  Alli- 
son and  Meighan  35  indicate  that  the  carbons,  particularly  anthracite 
activated  by  steam  at  700°  F.,  are  much  more  effective  than  silicious 
porous  substances,  such  as  pumice,  asbestos,  silica  gels,  porcelains  and 
glass  wool.  Although  the  work  of  these  investigators  and  others  shows 
that  chlorination  occurs  somewhat  below  300°  in  the  absence  of  cat- 
alysts, they  employed  temperatures  within  the  range  375°  to  400°  in 
nearly  all  of  their  experiments  with  catalysts. 

Ferric  chloride  and  antimony  pentachloride  give  poor  results  38 
but  the  work  of  the  U.  S.  Bureau  of  Mines  indicates  that  coke  impreg- 
nated with  iron  or  nickel  gives  the  highest  yields  of  chloroform,  that 
activated  carbons  give  the  best  yields  of  carbon  tetrachloride  and  that 
coke  impregnated  with  nickel,  tin  or  lead  gives  slightly  better  yields 
of  methyl  chloride,  using  larger  proportions  of  methane  in  the  latter 
case.  A  total  yield  of  about  90  per  cent  of  chlorinated  products,  based 
upon  the  gas  used,  can  be  obtained. 

Methyl  chloride  boils  at  —  23.7°,  melts  at  —  103°  ;  its  critical  tem- 
perature is  143°,  critical  pressure  66  atmospheres,  critical  density 
0.37.  The  densities  and  vapor  pressures  are  given  in  the  following 
table.87  The  latent  heat  of  evaporation  at  0°  C.  is  176  B.T.U.  per  Ib. 
or  98  kilogram-calories  per  kilogram,  or  4.94  kilogram-calories  per 
gram  molecule.37 

The  reduction  of  carbon  tetrachloride  to  chloroform  by  zinc  and  a 

*°J.  Soc.  Chem.  Ind.  32,  742  (1913). 
11  U.  S.  Pat.  888,900. 
82  U.  S.  Pat.  220,397. 


«"Loc.    cit. 

MPfeifer,  Mauthner  &  Reitlinger,  ,J.  orakt    Chem    (2)    w    23Q   no-iot 

«  Hoist,  Refrigerating  World,  1919,  May^p    13  W'      '       9          19)' 


THE  PARAFF1NE  HYDROCARBONS  81 

DENSITY  AND  VAPOR  PRESSURE  OP  METHYL  CHLORIDE. 

Density,  referred  Pressure,  absolute 

°C  to  water  at  30° F.  in  atmospheres 

-50                                               0.27 

-40  1.024  0.47 

-22  1.008  0.76 

-11  1.000  1.00 

-  4  0.991  1.16 

-  0  0.987  1.27 
+14                                             0.972  1.73 
+32                                              0.995                                               2.49 

40  0.945  2.91 

50  0.936  3.51 

60  0.925  4.20 

68  0.915  453 

90  0.892  6.91 

100  0.883  7.96 

little  aqueous  hydrochloric  acid 38  and  by  finely  divided  iron  in  the 
presence  of  water 39  has  been  carried  out  and  some  such  method  ap- 
pears to  offer  the  best  solution  thus  far  proposed  for  the  problem  of 
manufacturing  chloroform  from  methane. 

Tne  conversion  of  methane  into  hydrocyanic  acid  by  passing  a  mix- 
ture of  methane,  hydrogen  and  nitrogen  through  an  electric  arc  has 
been  tried  out  on  an  industrial  scale  but  details  of  the  process  have  not 
been  published.40 

Rideal  and  Taylor  have  reviewed  the  hydrogenation  of  carbon 
monoxide  to  methane.41  The  industrial  operation  of  the  process  would 
make  illuminating  gas  much  less  toxic  and  increase  its  calorific  value. 
The  process  might  be  of  value  in  localities  where  natural  methane  is 
not  available  and  where  the  methane  could  be  utilized  for  a  special 
purpose,  for  example,  the  manufacture  of  chlorinated  methane  prod- 
ucts. Elworthy 42  proposed  to  remove  the  carbon  dioxide  from  water 
gas,  add  hydrogen  sufficient  to  form  the  mixture,  CO  -J-  3H2,  and  effect 
the  conversion  to  methane  by  passing  over  catalytic  nickel  at  250°. 
At  one  time  Sabatier 43  attempted  the  industrial  solution  of  the  problem 
in  a  somewhat  different  manner.  He  noted  that  the  carbon  deposited 
from  the  conversion  of  CO  to  C02  and  carbon  at  500°  in  the  presence 
of  nickel,  readily  reacts  with  steam  to  form  C02  and  methane.  By 
superposing  the  two  reactions,  passing  water  gas  and  superheated  steam 
over  the  catalyst  at  500°,  mixtures  consisting  essentially  of  methane, 
hydrogen  and  carbon  dioxide  were  produced.  Reduced  nickel  at  250°- 

38  Chem.  Rev.  1896.  88. 

"A.  W.  Smith,  U.  S.  Patent,  753,325   (1904). 

«  Chem.  Abs.  1914,  1659. 

""Catalysis  in  Theory  and  Practice."    1919.    p.  182. 

«Brit.  Pat.  12,461   (1902)  ;  14,333  (1904). 

"French  Pat.  355,900    (1905). 


82        CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

300°  in  the  presence  of  an  excess  of  hydrogen  has  been  found  most  ef- 
fective,44 but  in  practice  considerable  difficulty  was  experienced  by 
poisoning  of  the  catalyst  by  substances  containing  sulfur,45  and  the  de- 
position of  carbon  on  the  catalyst  and  it  was  also  found  that  at  least 
five  volumes  of  hydrogen  are  required  for  one  volume  of  carbon  mon- 
oxide. Carbon  dioxide  is  reduced  to  methane  in  the  presence  of  nickel 
quite  rapidly  at  350°. 46  The  necessary  excess  of  hydrogen  can  be  ob- 
tained by  the  catalytic  conversion  of  CO  and  steam  to  hydrogen  and 
C02  and  removing  the  latter,  or  by  partially  separating  the  carbon 
monoxide  and  hydrogen  of  water  gas  by  liquefaction  methods.  Bed- 
ford finds  that  when  the  liquefaction  process  is  carried  out  so  that  the 
uncondensed  portion  contains  approximately  14  per  cent  carbon  mon- 
oxide, the  sulfurous  impurities  are  removed  with  the  liquefied  CO  and 
the  resulting  mixture  has  no  appreciable  poisoning  effect  on  the  cat- 
alyst. Bedford  carried  out  the  reaction  in  quartz  tubes  at  280°-300° 
and  owing  to  the  strongly  exothermic  character  of  the  reaction, 

CO  +  3H2 »  CH4  +  H20  +  48,900  calories,  the  reaction  maintains 

itself  without  external  heating.  In  order  to  prevent  the  deposition  of 
carbon  the  concentration  of  carbon  monoxide  was  kept  below  17  per 
cent,  the  resulting  gas  containing  28.3  to  31.8  per  cent  methane.  By 
successive  additions  of  carbon  monoxide  and  repassage  over  the  cat- 
alyst a  gas  mixture  containing  76  per  cent  of  methane  can  be  obtained. 
Meredith 47  states  that  it  is  difficult  to  prevent  the  formation  of  nickel 
carbonyl  in  this  process,  although,  as  is  well  known,  the  decomposition 
of  nickel  carbonyl  is  rapid  at  temperatures  as  low  as  200°  C. 

Ethane:  The  simple  derivatives  of  ethane  are  quite  familiar  to  all 
organic  chemists  and  their  reactions  have  been  most  frequently  em- 
ployed as  type  reactions  in  text  books  of  organic  chemistry.  Yet  ethane 
itself  has  never  been  a  product  of  industrial  interest,  and  the  hydro- 
carbon has  not  been  employed  as  the  raw  material  for  the  manufac- 
ture of  those  derivatives  which  are  so  important.  For  example,  ethyl- 
ene,  ethyl  chloride  and  ethyl  ether  are  all  manufactured  from  ethyl 
alcohol.  Changed  economic  conditions  conceivably  may  change  a  great 
many  of  these  processes.  That  ethane  can  be  separated  in  quite  a  pure 
state  from  methane  and  propane,  was  first  shqwn,  in  an  analytical  way, 
by  Burrell,  Seibert  and  Robertson,48  who  made  use  of  the  large  differ- 

44  Jochum,  J.  Gaslel,  57,  73,103,124   (1914). 
"Gautier,  Compt.  rend,  150,  1564    (1910). 

46  Sabatier  &  Senderens,  Compt.  rend,  13L,  514.  689   (1902)  :  Farbwerke  M.  L.  &  Br. 
Brit.  Pat.  146,110;  146,114   (1920). 

47  Gas  Age,  47,  7   (1921). 

48  U.  S.  Bureau  of  Mines,  Techn.  Paper  104   (1915). 


THE  PARAFFINS  HYDROCARBONS 


83 


ences  of  th'e  vapor  pressures  of  these  several  hydrocarbons  at  low  tem- 
peratures. 

By  the  Linde  or  Claude  methods  of  fractional  distillations  at  low 
temperatures  these  gases  may  be  easily  separated ;  in  fact,  the  separa- 
tion of  nitrogen  and  oxygen  is  considerably  more  difficult.  Reference 
to  the  boiling-points  of  these  several  substances  indicates  this  possi- 
bility. 

Boiling-Point,  at  760  mm.    Difference 

Nitrogen    —195.84°)  1Ofi,0 

Oxygen    -182.99°  \ 

Methane    —160.    °  »  7ft7o 

Ethane49    —  89.3  °  f 

Propane80    —44.1°  452° 

The  following  vapor  pressure  curves  of  liquid  ethane  were  deter- 
mined by  Burrell  and  Robertson,  Fig.  I,  and  by  Maas  and  Mclntosh, 
Fig.  II.  Natural  gas  and  possibly  oil  gas  and  petroleum  still  gases 

ETHANE 


-/oo* 


-//ol 


VAPOR 

FIG.  2. 


70 


contain  ethane  in  quantities  sufficient  for  its  separation  on  a  large 
industrial  scale;  the  high  ethane  content  of  many  samples  of  natural 
gas,  as  determined  by  the  old  method  of  combustion  and  calculation, 
is  undoubtedly  inaccurate,  as  has  been  previously  pointed  out,  but  10 


49  This  value  found  by  Burrell  &  Robertson,  J.  Am.   Chem.  Soc.  37,  1893   (1915)  ; 
Maas  &  Mclntosh  give  — 88.5°  as  the  boiling-point  of  ethane,  J.  Am.  Chem.  Soc.  36, 

10,  497   (1913)  ;  found  the  value  — 84.1° ; 
give  the  value  —  88.3°. 
(1915). 


Aiaas  &  Aicintosn  give  — s».o-  as  tne  Domng-pomt  or 

737    (1914)  ;  Cardoso  &  Bell,  J.  cMm.  phys.  10,  497    (1£ 

Maas  &  Wright,  J.  Am.  Chem.  Soc.  ^3,  1102   (1921)   giv« 

MBurreU  &  Robertson,  J.  Am.  Chem.  Soc,  37,  2188 


84        CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

to  12  per  cent  ethane  is  not  uncommon.  Practically  pure  ethane,  sepa- 
rated in  this  manner,  and  cheap  chlorine,  present  to  organic  chemists 
a  great  opportunity.  The  manufacture  of  ethyl  chloride,  ethylene, 
ethyl  ether  and  ethyl  alcohol  from  ethane  is  entirely  feasible  by  meth- 
ods now  known  but  which  are  capable  of  great  improvement. 

The  chemical  properties  of  ethane  are  nearly  identical  with  those 
of  methane ;  it  is  less  stable  to  heat  and  in  contact  with  metallic  nickel 


800 


TEMPER/JURE  -  DEGREES 
FIG.  1. 

at  325°  carbon  is  deposited  and  methane  and  hydrogen  are  formed.51 
It  is  absorbed  by  fuming  sulfuric  acid  somewhat  more  rapidly  than 
methane.52  Slow  oxidation  below  the  temperature  of  actual  ignition 
yields  chiefly  water,  carbon  dioxide,  carbon  monoxide  and  formalde- 
hyde.58 It  is  more  readily  chlorinated  than  methane  and  it  is  note- 
worthy, in  the  light  of  Michael's  positive  and  negative  theory  of  addi- 
tion, that  ethyl  chloride  on  further  direct  chlorination  yields  chiefly 
ethylidene  chlorine  but  in  the  presence  of  antimony  pentachloride 

n  Sabatier  &  Senderens,  Compt.  rend.  124.  1360   (1897). 
"Worstall,  J.  Am.  Chem.  Soc.  21,  249   (1899). 
"Bone  &  Stockings,  J.   Chem.  Soc.  85,  696    (1904). 


THE  PARAFFINS  HYDROCARBONS 


85 


ethylene  chloride  is  the  principal  product.54     No  researches  on  the 
chlorination  of  ethane  have  recently  been  published.55 

Propane:  The  principal  raw  materials  utilized  for  the  prepara- 
tion of  propane  and  its  simple  derivatives  are  acetone,  glycerine,  tri- 
methylene  glycol,  propyl  alcohol  from  fusel  oil,  and  propylene  from  oil 
gas  or  petroleum  still  gases.  Crude  pyroligneous  acid  contains  allyl 
alcohol,  but  no  industrial  use  for  it  has  been  found.  The  hydrocarbon 
itself  is  not  used  as  such  or  separated  from  natural  gas  or  other  gas 
mixtures  containing  it.  Natural  gas  is  the  only  source  from  which  it 


TEMPERATURE.  DEGREES 

could  be  separated  in  quantity.  For  laboratory  study  it  may  conveni- 
ently be  prepared  by  the  catalytic  decomposition  of  isopropyl  alcohol, 
over  alumina  at  380°-400°,  and  the  catalytic  hydrogenation  of  the  re- 
sulting propylene  to  propane.58 

The  vapor  pressure  curves  of  liquid  propane,  propylene  and  butane 
are  shown  in  the  accompanying  figure.57 

The  chiorination  of  propane  does  not  appear  to  have  been  studied 
since  the  work  of  Schorlemmer  58  in  1869,  who  noted  the  formation  of 
n. propyl  chloride  (?),  propylene  chloride  and  more  highly  chlorinated 
products.  Although  the  monochlorides  of  methane,  ethane,  pentane, 
and  probably  propane  and  butane  can  be  converted  into  the  corre- 

"D'Ans.  &  Kautzsch,  J.  prakt.  chem.  (2),  80,  3ie  (1909);  V.  Meyer  &  Miiller, 
Ber.  Zit,  4247  (1891)  ;  Kronstein,  Ber.  5$B,  I.  (1921). 

65  Cf.  Lacy,   U.   S.  Pat.  1,242,208  :   chlorinates  above   300°. 
88  Sabatier  &  Senderens,   Compt.  rend.  1*4,  1127    (1902). 
"Burrell  &   Robertson,  J.  Am.   Chem.  Soc.  SI,  2188    (1910). 
68  Ann.  152,  159  (1869). 


86        CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

spending  alcohols  with  good  yields  and  ethylene  chloride  may  be  con- 
verted satisfactorily  to  the  glycol,  the  more  highly  chlorinated  deriva- 
tive 1,  2,  3,  trichloropropane  behaves  very  differently.  Caustic  alkali 
yields  p-epidichlorohydrine  CHC1  =  CH .  CH2C1  and  a-derivative 
CH2  =  CC1 .  CH2C1,  and  alcoholic  potash  gives  ethylchloroallyl  ether, 
C2H50 .  C3H4C1.  From  what  is  known  of  the  halogen  derivatives  of 
propane,  it  is  very  improbable  that  glycerine  will  ever  be  manufactured 
industrially  by  their  means.  Glycerine  can  be  synthesized  by  adding 
HOC1  to  allyl  chloride  and  hydrolysing  the  product,  but  when  it  is 
attempted  to  prepare  allyl  chloride  by  decomposing  propylene  chloride, 
the  principal  products  are  found  to  be  a  and  |3  chloropropylene. 

Butanes:  Normal  butane  was  made  by  Frankland  in  the  attempt 
to  isolate  the  hypothetical  ethyl  radical,  by  the  reaction  of  ethyl  iodide 
and  metallic  zinc.  It  has  been  prepared  in  a  very  pure  state  by  Le- 
beau  by  treating  n. butyl  iodide  with  sodium  amalgam  in  liquid  am- 
monia.59 Its  boiling  point  at  755  mm.  is  0.5° ;  critical  temperature  151° 
to  152°.  At  17°  and  772  mm.  pressure  one  volume  of  water  dissolves 
0.15  volumes;  chloroform  at  17°  and  768  mm.  dissolves  32.5  volumes  of 
the  gaseous  hydrocarbon. 

The  most  convenient  source  of  n .  butyl  compounds  is  n .  butyl  alco- 
hol from  which  a  large  number  of  simple  derivatives  may  readily  be 
prepared.60  This  alcohol  is  now  a  common  commercial  article,  being 
obtained  together  with  acetone  by  fermenting  starch  with  a  mould, 
Amylomyces  rouxii  studied  by  Fernbach  and  Strange,  and  by  bacteria, 
probably  Bacillus  granulobacter  pectinovorum,  the  latter  process  being 
developed  by  Weizmann.61  The  butyl  alcohol  produced  in  ordinary 
alcoholic  fermentation  and  appearing  in  the  fusel  oil  fore-runnings  is 
isobutyl  alcohol,  (CH3)2.CH.CH2OH. 

The  most  convenient  source  of  crude  butane  is  the  very  light  gaso- 
line separated  from  natural  gas  or  "casing  head"  gas.  Garner  and 
Cooper  have  described  the  isolation  of  crude  butane  from  this  source 
by  the  application  of  principles  now  well  known  in  the  industry.62 

Butlerow 63  pointed  out  that  two  isomeric  butanes  were  possible  and 
synthesized  isobutane  by  treating  acetyl  chloride  with  zinc  methyl, 
according  to  the  well-known  Butlerow  synthesis,  forming  the  car- 

"Bull.  Ac.  Roy,  Belg.  1908,  300. 

w  Kamm  &  Marvel,  J.  Am.  Soc.  1920,  299. 

91  Speakman,  J.  Soc.  Chem.  Ind.  38,  155  (1919)  ;  Weizmann,  Brit.  Pat.  4,845 
«lJS1^)o;-,Hernb^c^  &  stran&6'  Brit-  Pat.  14,607  (1915)  ;  Fernbach,  Biit.  Patents,  109,- 
960  (1917)  ;  15,203,  15,204  and  16,925  (1911). 

«TT.  S.  Pat.  1,  307,353   (1919). 

"Ann.  m,  1  (1867). 


THE  PARAFFINS  HYDROCARBONS  87 

CH3 

Isobutane :  >  CH  —  CH3 

CH3 

binol  (CH3)3C.OH.  This  was  converted  into  the  iodide  which  on  re- 
duction with  zinc  in  the  presence  of  water  gave  isobutane,  an  octane 
and  isobutylene. 

Isobutane  boils  at  — 10.5°  under  757  mm. ;  its  critical  temperature 
is  134°  to  1350.6* 

The  butanes  are  readily  chlorinated  by  moist  chlorine  at  ordinary 
temperatures.65  Bromine  reacts  much  less  readily  and  on  heating  with 
bromine  in  a  sealed  tube,  it  is  decomposed  forming  tetrabromethylene, 
Br2C  =  CBr2  as  one  of  the  products.66  Isobutylene  readily  combines 
with  hydrogen  iodide  to  form  tertiary  butyl  iodide. 

The  Pentanes:  Both  normal  and  isopentane  occur  in  petroleum,  at 
least  in  certain  petroleums  which  have  been  carefully  examined.  The 
difficulty  of  separating  these  two  hydrocarbons  by  fractional  distilla- 
tion is  well  shown  by  the  work  of  Young,67  whose  results  are  ex- 
pressed by  the  following  figure: 


Thirteen  very  careful  fractional  distillations  and  the  use  of  a  very  effi- 
cient fractionating  column  were  required  to  isolate  these  two  hydro- 
carbons in  fair  degrees  of  purity. 

The  vapor  pressure  curves  of  butane  n.pentane,  n.hexane,  n. hep- 
tane and  n .  octane  are  given  in  the  following  table :  68 

The  pentanes  are  chlorinated  very  much  more  readily  than  methane 
and  ethane,  i.  e.,  at  0°  in  diffused  daylight.  The  relative  stability  of 

84  Lebeau,  loc.  cit. 

«5Mabery  &  Hudson,  Am.  Chem.  J.  19,  244   (1897). 

"Weith,  Ber.  11,  2244  (1878). 

<"«/.  Chem.  Soc.  73,  906  (1898). 

"Anderson,  J.  Ind.  Eng.  Chem.  12,  547  (1920). 


88        CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

the  halogen  derivatives  of  the  series  methane  to  pentanes  inclusive  has 
already  been  noted. 

No  satisfactory  method  of  preparing  these  simple  hydrocarbons 
seems  to  have  been  developed.  The  preparation  of  n.pentane  by  heat- 
ing acetyl  acetone  with  concentrated  hydroiodic  acid  to  180°  and  by 
heating  pyridine  with  the  same  reagent  to  300°  has  been  suggested. 
The  action  of  amyl  or  iso-amyl  bromides  on  magnesium,  in  ether, 
probably  yields  a  little  amylene  and  decanes,69  but  since  n.pentane  or 
isopentane  can  easily  be  separated  from  these  by-products,  the  method 


of  decomposing  amyl  or  iso-amyl-magnesium  bromides  by  water  would 
undoubtedly  prove  the  most  satisfactory  method  of  preparing  these  hy- 
drocarbons in  a  pure  state.  By  the  reduction  of  iso-amyl  iodide  by 
zinc  fairly  pure  isopentane  can  be  prepared,70  and  Ipatiev  made  isopen- 
tane'by  the  hydrogenation  of  trimethyl  ethylene.71 

Tetramethylmethane,  C(CH3)4,  was  prepared  by  reacting  upon 
2.2-dichloropropane  with  zinc  methyl, 

CH3  CH3  CH3 

>CCl2  +  Zn(CH3)2 »         >C<         +ZnCl2 

CH3  CH3  CH3 

This  hydrocarbon72  is  remarkable  for  its  relatively  low  boiling 
point,  9.5°,  and  relatively  high  freezing-point,  — 20°. 

69  Cf.  Tschelinzeff,  J.  Russ.  Phys.-Chem.  Soc.  36,  549  (1903)  ;  Tiffeneau,  Compt.  rend, 
m,  481    (1904). 

™Frankland,  Ann.  74,  53    (1850)  ;   Just,  Ann.  220,  152    (1883). 
"Ber.  42,  2089  (1909). 
"Lwow,  Z.  f.  Chetn.  1810,  520. 


THE  PARAFFINS  HYDROCARBONS  89 

Aschan73  has  studied  the  chlorination  of  the  pentane  and  hexane 
fractions  of  petroleum  and  also  the  chlorination  of  isopentane,  which 
hydrocarbon,  Aschan  claims,  is  present  in  all  petroleums.  The  best 
yields  of  monochloropentanes  are  obtained  by  chlorinating  with  dry 
chlorine  but  moist  chlorination  leads  chiefly  to  the  formation  of  the 
two  possible  primary  chlorides,  small  proportions  of  secondary  chlo- 
ride and  no  tertiary  chloride.  Dry  chlorination  yields  all  four  pos- 
sible monochlorides  the  properties  of  which  are  given  by  Aschan  as 
follows: 

Boiling-Point     .     D^-r~ 
lo 

4-chloro-2-methyl  butane  99.  -102.°  0.8692 

3-chloro-2-methyl  butane  90.  -  93.°  0.8752 

l-chloro-2-methyl  butane  96.  -  99.°  0.8818 

2-chloro-2-methyl  butane  85.5-  88.°  0.8692 

The  primary  iso-amyl  chloride  made  from  natural  fusel  oil  is  con- 
verted almost  quantitatively  to  the  acetate  and  alcohol  by  heating  with 
alcoholic  potassium  acetate  at  200°.  Isopentyl  chloride  is  only  very 
slowly  acted  upon  by  2  per  cent  caustic  potash  at  60°-70°. 

The  Hexanes:  Like  the  pentanes,  normal  hexane  may  readily  be 
separated,  in  an  impure  state,  from  light  petroleum  distillates,  and  the 
preparation  of  pure  n .  hexane  depends  upon  standard  laboratory  meth- 
ods such  as  the  reduction  of  secondary  hexyl  iodide  (made  from  man- 
nite)  or  the  condensation  of  normal  propyl  iodide  by  metallic  sodium.74 

Like  pentane  it  chlorinates  readily  and  it  also  reacts  rapidly  with 
bromine  in  sunlight.  The  mixture  of  monochlorides  contains  about 
10  per  cent  of  the  1-chloro  compound  and  about  45  per  cent  each  of 
the  2  and  3  chloro  derivatives.75  Its  reactivity  to  the  halogens,  to 
fuming  sulfuric  acid,  to  nitration  by  the  dilute  nitric  acid  method,  and 
the  properties  of  the  simple  derivatives,  chlorides,  .alcohols,  amines, 
carboxylic  acid  derivatives,  etc.,  is  almost  identical  with  the  chemical 
behavior  of  cyclohexane. 

The  Heptanes:  Normal  heptane  enjoys  the  distinction  of  being  the 
only  saturated  hydrocarbon,  other  than  the  solid  paraffines  formed  by 
phytochemical  processes.  It  is  one  of  the  major  constituents  in  the 
volatile  oil  of  the  two  American  pines,  Pinus  sabiniana  and  Pinus 
jeffreyi,  and  also  occurs  in  the  "petroleum  nuts,"  Pittosporum  resini- 
ferum,  of  the  Philippines.  How  such  a  saturated  hydrocarbon  is 
formed  in  the  living  plant  is  entirely  obscure;  it  is  accompanied  by 

«  Chem.  Abs.  H,  3654   (1920). 

T*  Michael,  Am.  Chem.  J.  25.  421    (1901). 

"Michael  &  Turner,  Ber.  S9t  2153  (1906). 


90        CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

no  other  substances,  so  far  detected,  which  conceivably  could  have 
been  the  parent  substance.  Unsaturated  hydrocarbons,  the  terpenes, 
are  undoubtedly  formed  from  alcohols,  and  it  is  well  established  that 
such  decompositions  occur  in  the  leaves  of  plants.  Pine  needle  oils 
commonly  contain  borneol  and  other  alcohols  although  the  oleoresins  of 
these  pines,  when  finally  secreted  in  the  resin  ducts  of  the  stem,  con- 
tain only  resin  acids  and  unsaturated  hydrocarbons.  The  fact  that  this 
particular  hydrocarbon  is  one  of  an  odd  number  of  carbon  atoms  is 
also  most  unusual,  since  by  far  the  great  majority  of  the  hydrocarbons, 
sugars  and  alcohols,  fatty  acids  and  ketones  occurring  in  plants  contain 
an  even  number  of  carbon  atoms. 

Normal  heptane  probably  occurs  in  most  light  petroleum  fractions, 
as  in  commercial  gasoline.76  Its  separation  from  gasoline,  however,  in 
a  reasonably  pure  state  is  a  matter  of  the  greatest  difficulty.  The 
raw  material  which  has  been  employed  for  the  preparation  of  the  best 
known  derivatives  of  n. heptane  is  oenanthol  or  n.heptyl  aldehyde.77 
This  aldehyde  undergoes  the  usual  aldehyde  reactions,  yields  1 . 1-di- 
chloroheptane  by  treatment  with  PC15,  and  on  reduction  gives  n.heptyl 
alcohol  from  which  n.heptyl  chloride  can  be  made  by  the  action  of 
hydrogen  chloride.  This  is  the  only  one  of  the  four  possible  monochlor 
derivatives  of  n .  heptane  which  has  been  prepared  in  reasonable  purity 
and  identified  as  such.  Only  three  of  the  possible  17  dichlorides  are 
known,  i.  e.,  the  1-1,  4-4  and  1-7  derivatives.  Until  the  discovery  of 
the  Grignard  reaction  which  serves  to  build  up  any  desired  carbon 
structure  up  to  10  carbon  atoms  and  with  limitations,  larger  mole- 
cules, and  also  the  discovery  of  catalytic  hydrogenation  by  which 
means  unsaturated  hydrocarbons  may  be  readily  converted  at  low  tem- 
peratures and  in  neutral  reaction  media,  to  saturated  hydrocarbons,  our 
knowledge  of  hydrocarbons  of  the  paraffine  series  containing  more 
than  six  carbon  atoms  was  very  limited  indeed. 

The  physical  properties  of  the  known  isomeric  heptanes  are  as 
follows: 

Name  Structure  Boiling-Point     Density 

n. Heptane  CH3(CH2)5CH3  98.2-98.5°        0.7006-  0° 

2-Methylhexane  (CH8)aCH.(CH2)3.CH3  89.0-90.4°        0.7067-  ^ 

9ft  ° 

3-Methylhexane  C3H7.CH(CH3).C2H5  90.  -92.  °        0.6865-^ 

"Young,  J.  Chem.  Soc.  73,  906  (1898)  ;  Engler  &  Hofer,  "Das  Erdol,"  Vol.  I,  244 
(1913). 

77  This  aldehyde  is  readily  prepared  by  the  well  known  method  of  destructive 
distillation  of  castor  oil,  enanthol  and  undecylenic  acid  being  formed. 


THE  PARAFFINE  HYDROCARBONS  91 

Name  Structure  Boiling-Point      Density 

3-Ethylpentane  CH.(C2HS),  95.  -98.  °        0.689  -27° 


2,  2-Dimethylpentane        (CH^CAH,  78.°  0.6910 

2,  4-Dimethylpentane        (CH3)2CH.CH2.CH.(CH,)3  83.  -84.  °        0.7002    5! 

3,  3-Dimethylpentane        (CH3)2C(C2HB)2  86.  -87.  °        0.7111    0° 

The  Octanes:  Normal  octane  probably  occurs  in  most  light  petro- 
leum distillates,  or  gasolines.  It  is  most  readily  prepared  in  a  pure 
state  by  treating  n.  butyl  iodide  with  sodium,78  a  reaction  which  is  said 
to  give  better  yields  with  alkyl  halides  of  higher  molecular  weight  than 
with  the  simpler  ones.  As  typical  examples  of  methods  which  may  be 
employed  in  the  synthesis  of  hydrocarbons,  the  methods  employed  in 
the  preparation  of  the  known  octanes  are  given  in  reaction  outline,  as 
follows: 

(1)  Normal  octane.78 

2CH3CH2CH2CH2I  +  2Na  -     —  >  Nal  +  CH3  (CH2)  6  .  CH3 

(2)  2-Methylheptane.™ 

CH3  CH2CH2CH3 

>CH.CH2CHO  +  Mg<  -  > 

CH3  X 

CH3 

>  CH  .  CH2CH  .  CH2CH2CH3 
CH3  | 

OH 

-  >  corresponding  iodide  -    —  >  2-methyl-heptane,  by 
reduction  with  copperized  zinc  and  hydrochloric  acid. 

(3)  8-Methylheptane*0 

CH3CH,CH2I  +  CH3COCH.C02C2H5- 

Na 

10%  KOH 

CH3COCH  .  C02C2H5  -     —  »  CH3COCH2CH2CH2CH, 


CHSC  (OH)  .  CH2CH2CH2CH3  --  »  corresponding  iodide- 


C 


2H5 


3-methylheptane,  by  reduction  as  indicated  above. 


"Zincke,  Ann.  152,  15   (1869). 

™L.  Clarke,  J.  Am.  Chem.  Soc.  SJ,  108   (1909). 

80  IMd.,  558  (1909). 


92        CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

(4)  4-Methylheptane.81 

CH3CH2CH2CH .  CH3  +  CH3COCH .  C02C2H5 > 

I  Na 

10%  KOH 

CH3COCH .  C02C2H5  -»  CH3CH2CH2CH .  CH2COCH3 

^01^    OTT  f^TI  OTT  /^TT 

3V_yXl .  V^Xl.2v>'JH2l^/Xl.3  v_y.LJ-3 

by  reduction  by  sodium  in  moist  ether >  alcohol 

-*  iodide  -    — »  CH3CH2CH2  —  CH  —  CH2CH2CH3 

CH3 

(5)  2 . 4-Dimethylhexane82 

CH3 
CH3CO .  CH2CH .  CH2CH3  +  Mg<         -> 

CH3 
CH3C  (OH)  .CH2CH .  CH2CH3 

CH3  CH3 

— > iodide,  which  by  reduction >CH3CH.CH,CH.CH2CH3 

CH3        CH3 

(6)  2.5-Dimethylhexane.    (Di-isobutyl) 

(a) 83    2 (CH8)  2CH ,  CH2I  +  2Na  -»  (CH8)  2CH .  CH2CH2CH  (CHa)  2 
(b)84    CH3CO.CH.C02C2H6 

CH3 

H2CH<        -^  CH3CO .  CH2CH2CH .  CH3 
CH3  | 

CH3 

CH3 
by  Mg<         ->  CH3C  (OH) .  CH2CH2CH .  CH3 

I  — >  hydrocarbon 

CH3  CH3  as  above 

,     81L.  Clarke,  Am.  Chem.  J.  89,  87   (1908)  ;  Ber.  40,  352    (1907)  ;  cf.  Clemmensen, 
Chem.  Ala.  6,  2919  (1912). 

«L.  Clarke,  J.  Am.   Chem.   Soc.   SO,  1144    (1908). 

MWurtz,  Ann.  96,  365    (1855). 

84  L.  Clarke,  J.  Am.  Chem.  Soc.  SI,  586  (1909). 


THE  PARAFFINS  HYDROCARBONS 


93 


(7)  3.  4-Dimethylhexane.85 

2CH3CH2COCH3  (Methylethyl  ketone)  ->  2CH3CH2CH(OH)  .CH3 

^2CH3CH2CH.CH3 

|  +  2N 

CH3  CH 

(8)  2-Methyl,  S-ethylpentane8* 


CH3CH2CH  .  CH  .  CH2CH3 


CHCH; 


CH 


>CH.COCH3  +  Mg< 


by  methods  given  above  — »  CH3CH, 


>CH.C(OH).CH, 
CH3CH2 

CH3 

CH, 


>CH.CH< 

tCH3CH2  CH3 

))     2.2.3.  S-Tetramethylbutane*7 
(CH3)3C.Br+  (CH3)3C.MgBr >MgBr2+  (CH3)3C-C(CH3) 
ighteen  isomeric  octanes  are  theoretically  possible. 
The  physical  properties  of  the  known  octanes  are  as  follows: 


Name 
n .  Octane 

2-Methylheptane 
3-Methylheptane 

4-Methylheptane 
2 . 4-Dimethylhexane 

2 . 5-Dimethylhexane 
3 . 4-Dimethylhexane 


2-Methyl,  3-ethylpen- 
tane 

2.2.3.3.-tetramethyl- 
butane 


Structure 
CH3(CH2)6CH, 

(CH3)2CH.(CH2)4CH, 


Boiling-Point      Density 

no 


I 

V^/flg 


CH3 

C2H5CH.CH2CHCH3 

CH,       CH, 
(CH3)2CH.CH2CH2CH(CH3)2    108.3°-108.5 


125.8° 
116.  ° 

0.7185^o- 
0.7035  -[f; 

117.6° 

0.7167^ 

118.  ° 

0.7217i£ 

109.8°-110.  ° 

0.7083  15! 
15° 

0.6993 


C2H5.CH.CH.C2HS 
CH3CH3 


116.  °-116.2°     0.7165 


15C 


CH  C  H 

(CH3)3C.C(CH3)3 


114.  ° 
106.  M07. 


0.7084^ 


E 


'Remarkable  for  its  high   melting-point.  103°-104°. 

Norris  &  Green,  Am.   Chem.  J.  26,  313    (1901). 
L.  Clarke,  Am.   Chem    J.  39,  572   (1908). 
87  Henry,  Compt.  rend.  142,  1075   (1906). 


94        CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

The  Nonanes  and  Decanes:  Pure  normal  nonane  boils  at  149.5° 
and  n.decane  at  173°.  The  petroleum  fraction  boiling  chiefly  at  150°- 
170°,  therefore,  consists  chiefly  of  these  two  hydrocarbons,  when  de- 
rived from  petroleums  of  the  Pennsylvania  type.88  This  particular 
fraction  is  a  regular  commercial  article,  being  sold  as  a  turpentine  sub- 
stitute. Its  volatility  or  rate  of  evaporation  and  solvent  power  for  oils 
and  resins  is  practically  identical  with  that  of  turpentine.89 

CH3 
2.6-Dimethyl  Octane,          >CH.  (CH2)3CH.CH2CH3 

CH3  | 

CH3 

is  of  interest  in  that  it  possesses  the  carbon  structure  of  the  aliphatic 
so-called  terpenes,  myrcene  and  ocimene,  C10H16,  and  also  the  alcohols 
geraniol,  linalool  and  citronellol  and  their  corresponding  aldehydes. 
Many  of  the  terpenes  proper  and  their  alcohols  are  very  probably  re- 
lated genetically  to  these  alcohols  and  aldehydes  and  it  is  therefore 
a  matter  of  theoretical  interest,  what  substance  or  substances  in  living 
plants  yield  alcohols  or  hydrocarbons  of  the  carbon  structure  of 
2.6-dimethyl  octane.  This  saturated  hydrocarbon  has  not  been  found 
in  nature  but  is  readily  made  by  hydrogenation  of  myrcene  or  ocimene, 
or  the  alcohols  geraniol  or  linalool.90 

Paraffines  C1QH22  to  C60#122.  Of  the  hydrocarbons  of  this  series 
all  the  normal  paraffines  up  to  C26H54  are  known,  and  also  a  few  hydro- 
carbons higher  in  the  series  have  been  definitely  characterized.  Most 
of  what  is  known  of  the  synthesis  of  the  solid  paraffines  is  found  in 
three  papers  published  by  Krafft,91  who  employed  the  following  meth- 
ods in  their  preparation: 

(1)  yP*  with   hydriodic   acid   and   phosphorus,   in   sealed 


Prprr  ^     oeS  meanS   °     ^oium. 

Preparation  of  ketones  by  heating  the  calcium  salts  of  fatty  acids;  con- 
InTphosphorls'  '  tO  dichlorides  b^  PC1<  and  reduction  by  HI 

wHssCO  .  C6Hi3  _»  dichloride  —  >  hydrocarbon 

-  ™>  419,  482   (1897). 
over          range  ^n^eiSwy  abo^^?!  ^  ^  Varnish  boils  chieflr 


of   oan, 

linseed  oil.     However,  the  difference  in 

tblgned  witt  fresh,, 


oxidation    or    "drying"    of 


<1908)- 


THE  PARAFFINS  HYDROCARBONS  95 

Peterson 92  employed  the  method  of  electrolysing  the  fatty  acid 
soaps  and  Mai 93  heated  the  barium  soaps  with  sodium  methoxide. 
Formates  at  290°-300°  94  decompose  to  paraffines. 

Crystalline  paraffines  have  been  noted  from  a  wide  variety  of 
sources  but  commercial  paraffine  is  derived  principally  from  certain 
petroleums  and  to  a  lesser  extent  from  shale  oil,  ozokerite,  and  the  dis- 
tillates obtained  by  the  carbonization  of  coal  or  lignite  at  low  tempera- 
tures. The  constitution  of  the  paraffines  made  by  synthesis  according 
to  the  methods  indicated  above,  may  reasonably  be  inferred  from  the 
methods  employed  in  their  preparation,  but  as  regards  the  crystalline 
paraffines  found  in  the  various  pyrolytic  distillates  and  in  natural 
waxes  and  essential  oils  we  know  practically  nothing  more  than  may 
be  inferred  from  their  melting-points,  and  these  values  may  be  very 
misleading.  Thus  Krafft95  prepared  a  series  of  paraffines,  by  frac- 
tional crystallization,  from  the  crude  paraffine  isolated  from  an  oily 
distillate  from  lignite.  On  the  basis  of  their  melting  points,  varying 
from  22.5°  to  76°,  the  various  crystal  fractions  are  described  as  eight- 
een distinct  substances  but  many  of  the  specimens  so  prepared  were 
probably  mixtures.  It  is  probable  that  many  of  these  crystalline  paraf- 
fines are  not  normal  hydrocarbons,  for  example,  n-eicosane,  C20H42, 
melts  at  36.7°  (made  by  condensing  n.decyl  iodide  by  sodium)  but  an 
isomeric  hydrocarbon  melting  at  69°  has  been  reported  from  four  dif- 
ferent natural  sources. 

It  is  of  interest  to  note  the  number  of  essential  oils  and  other  natural 
products  which  contain  solid  paraffines,  and  that  most  of  them  evi- 
dently bear  no  relation  to  the  natural  fatty  acids,  having  many  more 
carbon  atoms  than  these  acids. 

Source  Melting-Point 

Kaempferia  galanga  (about  50%  of  the  essential  oil)** 10.° 

(  Rose  oil   22.° 

j  Jaborandi  leaves * . "  28°-29.° 

I  Rose  oil  .."..!.*!.*.!..*  40°-41.° 

|  Birch  buds   '..'.'...*..'..'..'.'.'.'.  5o!° 

'  Camomile  oil   53°-54]° 

'  Orange  blossoms  ......!.!.....  55.° 

I  Eucalyptus  oils w '.'.'..  55°-56.° 

i  Sassafras  leaves   58.° 

Bees-wax ;  Virginia  and  Kentucky  tobacco 98  ...'.'. '. '. '. '. '. '.  1 '. .........'.  59.5° 

82  Z.  f.  Electroch.  12,  144    (1906). 
93  Ber.  22,  2134    (1889). 

•*  Fr.  Bayer  &  Co.  J.  Chem.  Soc.  A6s.  1918,  I,  209. 
™Ber.   40,  4779    (1907). 

66  Schimmel  &  Co.  Semi-Ann.  Rep.  1903,  I,  43. 

«  Smith,  Chem.  Aba.  8,  399  (1914)  ;  in  Eucalyptus  acervula,  E.  paludosa  and  E. 
smithn. 

98  Thorpe  &  Holmes,  J.  Chem.  Soc.  79,  982  (1901). 


96        CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

Source  Melting-Point 

Verbena    62.5° 

Arnica,  essential  oil ;  pelargonium  63.° 

Camomile,  Roman 63°-64.° 

Dill  oil;  Cistus,  several  species;  Chrysanthemum  cineraraefolium. . .  64.° 

Wintergreen  oil,  from  Betula  and  Gaultheria 65.5° 

Bees-wax;  leaves  of  European  olive;   Kentucky  and  Virginia  to- 
bacco; seeds  of  Brucea  sumatrana;  Lippia  scaberrina;   Micro- 

meria  chamissonis;  Grindelia  robusta;  Gymnene  sylvestre 68.1° 

Eriodictyon  calif ornicum ;  leaves  of  European  olive;  Arthusa  cyna- 

pium    74.7° 

Evodia  simplex   80°-81.° 

Paraffines  are  also  found  in  the  mineral  ozokerite,  which  is  mined 
near  Boryslaw,  Galicia,  and  in  Wasatch  and  Utah  counties,  Utah.  Re- 
fining of  ozokerite  by  concentrated  sulfuric  acid  yields  ceresine,  which 
is  valued  for  its  relatively  high  melting  point.  When  ozokerite  is 
distilled  crystalline  paraffine,  about  40  per  cent,  can  be  separated  from 
the  distillate,  and  the  undistilled  residue  is  ozokerite  pitch  or  "oko- 
nite."  Fractional  crystallization  of  the  solid  waxes  in  Galician  ozo- 
kerite gives  a  series  of  fractions  the  lowest  melting  at  about  54°  and 
the  highest  melting  at  92.8°-93.2°."  Practically  nothing  is  known  of 
the  nature  of  these  hydrocarbons  in  refined  ceresine  beyond  the  fact 
that  their  analyses  indicate  the  composition  CnH2m+2  and  that  their 
chemical  behavior  is  like  that  of  other  solid  parafiines. 

The  crystallization  of  paraffine  is  considerably  affected  by  the  vis- 
cosity of  the  oil  from  which  it  is  crystallized  and  also  the  presence  of 
asphaltic  matter  seriously  interferes  with  the  crystal  growth.  With 
increasing  viscosity  of  the  oil  solvent  the  crystal  size  diminishes.100 
The  exact  nature  of  the  so-called  "amorphous  wax"  is  not  known  but 
repeated  distillation  of  oils  containing  much  paraffine  yields  cleaner 
distillates  from  which  large  crystals  are  obtainable  without  difficulty. 
According  to  Rakuzin 101  crude  petroleums  contain  crystallizable  paraf- 
fine although  its  crystallization  is  greatly  interfered  with  by  asphaltic 
substances  present.  He  is  therefore  opposed  to  Zaloziecki's  views  as  to 
the  presence  of  "protoparaffine"  in  crude  petroleums,  but  there  is  no 
doubt  that  complex  substances  such  as  the  "kerogen"  of  oil  shale,  peat 
and  lignite,  yield  paraffine  only  when  decomposed,  as  by  heat. 

Paraffine  is  remarkably  insoluble  in  most  organic  solvents.  The 
solubility  of  a  paraffine  fraction,  melting-point  64°  to  65°  from  Ga- 
lician ozokerite,  in  petroleum  ether  is  as  follows:  102 

M  Engler,  "Das  Erdoel,"  Vol.  I,  667. 
'»°Cf.  Fuchs,  Petroleum  u,  1281   (1919). 

'• chem-  B°c A*-      ' 


THE  PARAFFINS  HYDROCARBONS  97 

g.  paraffine  in 
Solvent  100  g.  solvent 

Carbon  bisulfide  12.99 

Petroleum  ether,  boiling-point  below  75° 11.73 

Acetic  acid,  glacial 0.06 

Since  petroleum  ether  and  glacial  acetic  acid  are  miscible  in  all 
proportions,  these  two  solvents  are  recommended  for  recrystallizing 
paraffine.  In  industrial  practice  the  oil  and  low-melting  wax  is  per- 
mitted to  drain  slowly  from  the  crude  crystals  in  warm  chambers,  i.  e., 
the  "sweating  process." 

By  several  fractional  distillations,  at  40  mm.,  Mabery  103  separated 
commercial  paraffine  into  several  fractions,  the  lowest  melting  at  48° 
and  the  highest  at  62°-63°. 

The  dielectric  constant  of  paraffine  is  such  that  large  quantities 
are  used  for  the  purpose  of  electrical  insulation,  usually  in  cases  where 
the  material  is  not  subjected  to  temperatures  high  enough  to  melt  the 
wax.  Comparisons  of  the  dielectric  constant  of  paraffine  and  other 
common  insulating  materials,  are  as  follows:  104 

E 

Paraffine,  crude  brown  2.07 

melting-point  44°-46°  2.105 

"       54°-56°    ...: 2.145 

double  refined 1.94 

Asphalt    2.68 

Amber  2.80 

Shellac  3.10 

Gutta-percha 4.43 

Bees-wax 4.75 

The  specific  heat  of  paraffine  wax  is  a  linear  function  of  the  tem- 
perature; at  100°  it  is  0.6307,  at  0°  =  0.47,  at  — 100°  =  0.325  and  at 
- 180°  =  0.199.105  The  latent  heat  of  fusion  of  commercial  paraffine 
wax,  calculated  from  the  lowering  of  the  freezing  point  on  adding  sub- 
stances of  known  molecular  weight,  ranges  from  38.9  to  43.9  calories.106 

Paraffine  wax  is  generally  considered  to  be  a  very  inert  material  but 
it  is  attacked  by  nitric  acid  and  by  sulfuric  acid  at  slightly  elevated 
temperatures,  oxidation  rather  than  nitration  or  sulfonation  being  the 
principal  result.  It  reacts  readily  with  sulfur  on  heating  to  about  200°, 
evolving  hydrogen  sulfide ;  in  fact,  this  reaction  serves  as  an  admirable 
method  for  the  laboratory  preparation  of  hydrogen  sulfide,  particularly 
where  the  gas  is  not  continually  needed  and  the  apparatus  must  stand 

103  Cf.^m.  Chem.  J.  S3,  251  (1905). 

10*  Landolt-Bornstein,  "PJiysikalisch-Chemische  Tabellcn,"  1912,  pp.  1212. 
"•  Nernst,  J.   Chem.   8oc.  Abs.  108,  II,  263   (1910)  ;  Bushong  &  Knight,  J.  Ind.  A 
Eng.  Chem.  12,  1197   (1920). 

"•Kozicki  &  Pilat,  J.  8oc.  Chem.  Ind.  37,  681  A   (1918). 


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ic2    CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

idle 'for -long  periods.107  Chlorine  reacts  rapidly  when  passed  into  the 
'melted  wax  at*about  125°,  or  in  solution  in  carbon  tetrachloride.  Such 
a  chlorinated  product,  containing  about  33  per  cent  chlorine,  has  been 
employed  as  a  solvent  for  chloramine-T,  about  10  per  cent  of  this 
germicidal  substance  dissolving  in  the  "chlorocosane"  at  ordinary  tem- 
peratures.108 The  oxidation  of  paraffine  by  air  or  oxygen  at  120°-160° 
has  already  been  referred  to  (see  p.  52).  Paraffine  is  also  less  stable 
to  heat  than  is  sometimes  believed.  Distillation,  at  ordinary  pressure, 
of  a  wax  melting  at  52°  causes  a  decrease  in  melting-point  due  to  de- 
composition of  about  4°.  In  the  old  fashioned  cracking  process  as  car- 
ried out  to  increase  the  yield  of  kerosene,  the  wax  often  crystallizes 
from  the  distillate  in  fine  large  crystals,  due  largely  to  decrease  in  the 
viscosity  of  the  distillate,  but,  according  to  Mabery,109  paraffine  is  ac- 
tually decomposed  during  the  process. 

Notes  on  the  Refining  of  Petroleum  Distillates. 

Petroleum  distillates  are  refined  with  the  object  of  removing  offen- 
sive odors,  removing  or  lightening  the  color  and  also  rendering  the  oils 
more  stable  in  the  sense  that  certain  constituents  which  oxidize  readily 
with  darkening  of  color  and  formation  of  acids  or  resinous  substances 
are  removed.  The  physical  properties  of  the  various  fractions  are  but 
very  slightly  changed  by  refining,  unless  the  lowering  of  the  congealing 
point,  or  cold  test,  by  the  removal  of  paraffine  wax  may  be  considered 
as  a  refining  operation.  When  first  distilled  from  the  crude  oils  the 
lighter  fractions,  including  gasoline  and  kerosene,  are  nearly  free  from 
color  and  the  lubricating  oil  fractions  are  clear  shades  of  amber,  brown 
or  reddish  brown,  but  on  standing  in  contact  with  air,  unrefined  gaso- 
line and  kerosene  become  yellow  and  the  lubricating  distillates  become 
very  dark  in  color.  These  color  changes  do  not  take  place  appreciably 
in  well  refined  oils. 

Offensive  odors  are  generally  pronounced  in  the  case  of  the  more 
volatile  oils,  gasoline  and  kerosene,  particularly  when  these  are  made 
from  heavier  oils  by  pyrolytic  processes.  The  offensive  odor  of  these 
distillates  is  commonly  attributed  to  defines  but,  with  the  exception 
of  conjugated  di-olefines  such  as  cyclohexadiene  and  cyclopentadiene 
present  in  light  oil  gas  condensates,  the  odors  of  pure  unsaturated  hy- 
drocarbons are  mild  and  not  offensive.  The  conjugated  di-olefines 

!M  £uf],  °1L  °£  lu£rIcatinS  oil  also  gives  H2S  on  heating  with  sulfur. 

'Dakin  &  Dunham.  Chem.  Abs.  12,  1079  (1918). 
1MProc.  Am.  Phil  800.  1897,  135. 


THE  PARAFFINS  HYDROCARBONS  103 

have  a  sharp  irritating  odor  suggestive  of  allyl  alcohol  or  acrolein,  but 
less  pronounced.  Unsaturated  hydrocarbons  generally  develop  objec- 
tionable odors  on  long  standing  due  to  oxidation,  for  example  turpen- 
tine when  fresh  is  very  sweet  and  pleasant  in  odor,  deteriorates  by 
air  oxidation,  formic  acid  being  one  of  the  products  formed.  The  con- 
stituents which  are  chiefly  responsible  for  the  objectionable  odors  of 
petroleum  distillates  are  derivatives  containing  sulfur,  nitrogen  bases 
and  naphthenic  acids.  These  are  very  efficiently  removed  by  the  usual 
processes  of  refining  with  concentrated  sulfuric  acid  and  washing  with 
caustic  alkali,  although  special  methods  have  to  be  resorted  to  in  order 
to  remove  sulfur  derivatives  from  oils  derived  from  certain  crudes,  for 
example  the  Frasch  copper  oxide  method  as  applied  to  petroleum  of 
the  Lima-Indiana  field.  Nitrogen  bases  in  the  more  volatile  distillates 
possess  odors  closely  resembling  pyridine.  These  simpler  nitrogen 
bases  are  generally  absent  in  the  case  of  gasoline  and  kerosene  distilled 
directly  from  crude  petroleums,  but  are  present  in  pyrolytic  gasolines, 
unless  made  from  nitrogen  free  oil.  Petroleums  of  the  Mid-continent, 
Gulf  coast,  California  and  Mexican  fields  on  distilling  under  pressure 
yield  volatile  malodorous  nitrogen  bases.  Mabery  has  investigated  the 
nitrogen  bases  present  in  California  petroleum  and  concludes  that  they 
are  quinoline  derivatives.  When  light  distillates,  e.  g.,  motor  fuel  or 
kerosene,  containing  the  simpler  nitrogen  bases,  are  treated  with  cop- 
per oxide,  as  by  the  Frasch  method,  the  oxide  combines  with  the  or- 
ganic bases  and  treatment  of  the  resulting  copper  oxide  compound  with 
caustic  alkali  liberates  the  nitrogen  bases.  In  ordinary  practice,  how- 
ever, the  organic  bases  are  very  efficiently  removed  by  treating  with 
concentrated  sulfuric  acid.  When  the  acid  sludge  is  diluted  with  water 
to  precipitate  oil  and  tarry  matter,  salts  of  the  organic  bases  and  a 
large  proportion  of  the  alkyl  sulfuric  esters,  derived  from  the  unsatu- 
rated  hydrocarbons,  remain  in  solution  in  the  diluted  acid.  When  this 
diluted  acid  is  concentrated  by  the  usual  process  of  open  pan  heating 
and  evaporation,  this  dissolved  organic  matter  carbonizes  and  causes 
the  destruction  of  a  portion  of  the  acid.  The  charring  of  this  organic 
matter  with  the  separation  of  carbon  seriously  interferes  with  the  oper- 
ation of  cascade  evaporating  systems  by  clogging  of  the  overflow  lips. 
The  tarry  matter  precipitated  by  .diluting  the  sludge  derived  from 
treating  lubricating  oils,  also  generally  contains  nitrogen  bases,  as  can 
readily  be  shown  by  heating  or  distilling  with  an  excess  of  lime,  but 
the  quantity  of  ammonia  thus  obtainable  is  too  small  to  be  of  indus- 
trial interest. 


104      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

Sulfuric  acid  is  also  very  effective  in  removing  naphthenic  acids, 
as  was  first  shown  by  Zaloziecki,144  and  Gurwitsch 145  later  showed  that 
this  removal  of  naphthenic  acids  is  not  merely  a  solution  effect  and 
that  far  greater  proportions  of  the  naphthenic  acids  present  pass  into 
the  acid  layer  than  corresponds  to  the  proportions  required  by  the 
law  of  partition  coefficients.  These  observations  are  in  accord  with  the 
findings  of  Kendall  and  Carpenter  who  showed  that  a  very  wide  variety 
of  organic  substances  containing  oxygen,  e.  g.,  aliphatic  and  aromatic 
acids,  ketones,  aldehydes,  and  phenols,  form  addition  products  with 
concentrated  sulfuric  acid  and  they  regard  these  addition  products  as 
oxonium  compounds.  American  petroleums  do  not  contain  conspicu- 
ous proportions  of  naphthenic  acids,  as  do  most  of  the  Russian  oils, 
but  many  of  the  Gulf  Coast  oils  contain  naphthenic  acids  of  high 
boiling-point.  These  high  boiling  naphthenic  acids  are  removed  from 
the  lubricating  oil  distillates  by  alkali.  They  are  nearly  odorless  and 
their  alkali  soaps  are  very  easily  salted  out  of  solution  on  account  of 
their  large  molecular  weight.  They  have  apparently  not  been  investi- 
gated and  nothing  definite  regarding  their  empirical  composition  or 
chemical  character  is  known.  They  are  not  recovered  in  present 
refinery  practice. 

Practically  nothing  is  known  of  the  nature  of  the  coloring  matters 
in  petroleum  distillates.  When  such  oils  darken  by  air  oxidation,  amor- 
phous asphalt-like  substances  are  formed.  Sulfuric  acid  is  very  ef- 
fective in  removing  coloring  matter,  which  is  readily  understood  if  the 
coloring  matter  consists  largely  of  substances  containing  oxygen  or 
nitrogen.  It  is  improbable  that  these  coloring  matters  are  hydro- 
carbons, since  the  few  colored  hydrocarbons  which  are  known  contain 
conjugated  unsaturated  groups,  as  in  the  hydrocarbons  of  the  fulvene 
series.  Some  writers  regard  the  removal  of  such  coloring  matter  by 
sulfuric  acid  as  a  purely  physical  or  colloid  phenomenon.146  However, 
as  all  refiners  know,  it  is  necessary  to  use  concentrated  sulfuric  acid 
in  order  to  hold  the  tarry  matter  in  solution,  since  in  addition  to  the 
small  amount  of  coloring  matter  present  in  the  original  unrefined  lubri- 
cating oil,  constituents  are  present  which  yield  tar  on  treating  with 
acid.  Although  water  white  gasoline  and  kerosene  can  be  made  with- 
out great  difficulty,  it  is  impossible  entirely  to  remove  the  color  from 
lubricating  oils  by  sulfuric  acid  (or  oleum)  and  alkali  treatments. 

144  Ghem.  Ztg.  1892,  905. 

]«£  I  PKvsM-  Ghem.  87,  323  (1914). 

148  Ubbelohde,  Petroleum,  4,  1395  ;  Schulz,  Petroleum,  5,  No.  4  and  8. 


THE  PARAFFINS  HYDROCARBONS  105 

Pale  yellow  viscous  oils  can  be  made  in  this  way  which  are  practi- 
cally tasteless  (liquid  paraffine  oil)  but  filtration  through  fuller's147 
earth,  bone  black  or  similar  material,  or  distillation  in  vacuo,  must  be 
resorted  to  in  order  to  obtain  colorless  oil  such  as  is  desired  for  phar- 
maceutical purposes. 

The  fluorescence  of  petroleum  distillates  is  due  to  substances  which 
are  largely  removed  by  sulfuric  acid,  although  several  treatments  with 
concentrated  acid  followed  by  treatments  with  oleum  (15%  S03)  are 
necessary  entirely  to  remove  them.  This  property  also  has  been  re- 
garded by  some  writers  as  being  due  to  particles  of  sulfur,  carbon 
or  other  substance  in  a  colloidal  degree  of  dispersion,  or  due  to  the 
presence  of  substances  having  extremely  large  molecules.  Although 
such  mixtures  are  not  optically  homogenous  and  do  show  pronounced 
Tyndall  effects,  true  fluorescence  is  not  observed  in  aqueous  or  oil 
suspensions.  Most  petroleum  distillates  and  certain  crude  petroleums 
which  are  sufficiently  free  from  asphaltic  matter,  such  as  light  Penn- 
sylvania crudes,  exhibit  green,  bronze-green,  bluish  green  or  clear  blue 
fluorescence.  Examination  of  carefully  filtered  fluorescent  oils  in  a 
quartz  ultramicroscope  of  the  Zsigmondy  type  shows  no  particles  in 
suspension.148  When  sulfuric  acid  sludge  is  diluted  with  water  and 
filtered  to  remove  oil  and  tar  the  resulting  aqueous  solutions  are  usu- 
ally highly  fluorescent.  In  other  words,  the  fluorescent  substances 
have  been  sulfonated  to  water  soluble  sulfonic  acids.  It  is  probable, 
therefore,  that  the  extremely  small  quantities  of  fluorescent  substances 
which  are  present  in  petroleum  are  highly  condensed  or  benzenoid  hy- 
drocarbons.149 Such  fluorescent  substances  are  commonly  formed  when 
any  organic  substance  is  charred,  for  example,  boiled  linseed  oil  ex- 
hibits fluorescence  if  even  slight  carbonization  occurs  during  the  boiling 
process.  The  heavy  waxy  distillates  obtained  toward  the  end  of  the 
heating  of  an  old-fashioned  coking  still  are  highly  fluorescent. 

For  various  trade  reasons  it  is  sometimes  desirable  to  modify  the 
fluorescence  and  so-called  "de-blooming"  reagents  are  sometimes  added 
to  the  oil.  Thus  nitronaphthalene  is  sometimes  employed  for  this  pur- 
pose. It  is  well  known  that  the  fluorescence  of  all  organic  substances 
which  possess  this  property  is  greatly  modified  by  various  solvents 

147  It  is  probable  that  the  color  absorbing  qualities  of  fuller's  earth  are  dependent 
upon  the  presence  of  partially  dehydrated  amorphous  silica.  Certain  American  refin- 
eries have  recently  manufactured  a  bleaching  material  superior  to  fuller's  earth, 
by  treating  natural  talc-like  hydrated  silicates  with  sulfuric  acid,  washing  neutral 

f«  «vatl,n*  by  dryinS  at  not  too  high  temperatures. 

«5£°° ks  and  Bacon,  J.  Ind.  &  Eng.  Chem.  6,  623    (1914). 

*u  *  ?hat  the  fluorescent  constituents  are  not  nitrogen  derivatives  is  indicated  by 
the  fact  that  80%  sulfuric  acid  does  not  remove  them. 


106       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

and  the  fluorescence  of  petroleum  is  affected  by  the  common  solvents  15° 
in  a  way  entirely  parallel  to  the  findings  of  Kauffman 151  in  the  case 
of  the  diaminoterephthalic  acid  methyl  esters.  Carbon  bisulfide,  nitro- 
benzene, and  aniline  diminish  the  intensity  of  the  fluorescence  and 
change  its  original  bluish  green  character  to  dull  green.  Amyl  alcohol 
and  petroleum  ether  intensify  the  fluorescence  and  enhance  its  bluish 
character.  Filtration  of  oils  through  fuller's  earth  does  not  remove  the 
fluorescent  constituents  appreciably.  Oxidizing  agents  destroy  the  con- 
stituents in  question  and  sun-bleached  oils  which  have  thus  been  sub- 
jected to  air  oxidation  are  considerably  altered  in  this  respect,  usually 
acquiring  a  brownish  green  or  muddy  fluorescence. 

The  per  cent  of  sulfur  in  the  various  petroleum  fractions  is  very 
greatly  reduced  by  treating  with  concentrated  sulfuric  acid,  except 
in  the  case  of  highly  unsaturated  pyrolytic  distillates  when  treated 
with  a  relatively  small  quantity  of  acid,  in  which  case  an  increase  in 
sulfur  content  may  be  observed.  This  is  due  to  the  formation  of  neu- 

RO 
tral  esters  of  the  type        >S02.    No  real  explanation  of  the  removal 

RO 

of  sulfur  compounds  from  mineral  oils  by  sulfuric  acid  can  be  ad- 
vanced since  our  knowledge  of  the  nature  of  these  substances  is  so 
meager.  Mabery  and  Smith182  found  that  on  treating  a  distillate 
from  northern  Ohio  oil  with  sulfuric1  acid  the  sulfur  content  was  re- 
duced from  0.51%  to  0.13%,  and  according  to  Robinson153  sulfuric 
acid,  98%  H.S04,  is  much  more  effective  than  ordinary  acid,  a  certain 
Ohio  distillate  containing  0.346%  sulfur  being  thus  refined  to  0.05% 
sulfur. 

The  reactions  of  sulfuric  acid  and  pure  olefines  of  different  types 
have  been  discussed  in  another  section.  It  is  there  shown  that  the 
hydration  of  the  olefines  to  alcohols  is  important  only  with  ole- 
fines of  four  to  eight  carbon  atoms  and  that  on  standing  in  contact 
with  the  acid  the  proportion  of  polymers  increases  and  the  yield  of 
alcohols  decreases.  With  olefines  of  ten  or  more  carbon  atoms  and 
containing  one  double  bond,  polymerization  is  the  principal  result;  in 
certain  instances  being  practically  quantitative.  In  so  far  as  the 
polymerizing  action  of  sulfuric  acid  on  unsaturated  hydrocarbons  is 
concerned,  the  specific  gravity  and  viscosity  of  petroleum  distillates 
should  be  increased  by  refining.  Usually  a  slight  decrease  in  these 

180  Brooks  &  Bacon,  loc.  cit. 
151  Ann.  393,  1    (1912). 
"'Am.   Chem.  J.  189^  88. 
1U  Ohem.  Ztg.  Rep.  1907,  194. 


THE  PARAFFINS  HYDROCARBONS  107 

values  is  observed  after  refining  in  this  way,  particularly  in  the  case 
of  lubricating  oils.  The  effect  of  refining  on  the  specific  gravity  of  a 
number  of  pyrolytic  gasolines,  made  by  distillation  of  heavier  oils 
under  pressure  of  100  to  150  pounds  is  indicated  in  the  following:  154 

25° 

Specific   Gravity 

25° 

Loss  on  refining, 

Original  gasoline                                After  refining  %  by  volume 

0.739                                               0.743  9.0 

0.729                                               0.735  S3 

0.727                                               0.748  9.8 

0.737                                                0.754  10.1 

0.730                                               0.749  10.6 

Such  oils  refined  and  washed  in  the  usual  way  become  discolored  on 
standing  a  few  weeks,  but  if  they  are  redistilled  after  refining,  this 
discoloration  does  not  take  place,  at  least  by  no  means  rapidly.  Such  a 
redistillation  also  may  serve  the  purpose  of  removing  the  heavy  oily 
polymers  formed  by  the  acid  treatment  and  which  are  commonly  be- 
lieved to  be  objectionable  constituents  of  gasoline  when  used  as  motor 
fuel  or  for  extraction  or  cleaning  purposes. 

One  of  the  effects  of  treating  highly  unsaturated  oils  with  relatively 
small  proportions  of  sulfuric  acid  is  to  form  alkyl  sulfuric  esters  which 
remain  dissolved  in  the  oil  and  are  not  washed  out  by  alkali.  This  is 
shown  in  the  following  treatment  of  a  mixture  of  hexenes: 

SULFURIC  ESTERS  IN  REFINED  HEXENE. 

Vol.  Residual               g.  SO,  on  %  Cole,  as 

Vol.  Oil  cc.           VoLH2SOiCC.            OiLcc.              Distillation  (RO)£O> 

50                         25                          32                          0.284  4.9 

50                          50                          28                          0.146  2.9 

50                         100                          26                           0.094  1.8 

The  concentration  of  the  sulfuric  acid  employed  has  a  marked  effect 
upon  the  sulfur  thus  introduced,  as  is  shown  by  the  following  results  of 
Condrea,155  on  a  Roumanian  kerosene,  refined  by  a  2%  volume  of  acid 
at  20°: 

Acid  concentration..  90%  95%  97%  100%  5%  SO,  10%  SO,  20%  SO. 

Color  mm.  to  stand- 
ard    135  175  230  290  285  270  240 

S02.g.  per  1  liter....  0.157  0.294  0.426  0.67  1.30  1.71          257 

Sulf  onic  acids  in  acid 

tar  1.30  2.57  4.20  7.30  12.45  16.77  35.00 

Refining  with  sulfuric  acid  at  low  temperatures  greatly  reduces  the 
oxidizing  effect  of  the  acid,  with  less  attendant  tar  and  color  formation. 

1M  Brooks  and  Humphrey,  loc.  cit 
luRev.  petrol.  1911,  61. 


108      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

It  is  well  known  that  lighter  colored  oils  are  produced  by  operating  at 
low  temperatures,  but  some  difference  of  opinion  exists  as  to  the  effi- 
ciency of  the  refining  in  other  respects.  Zaloziecki 156  gives  the  follow- 
ing data  obtained  by  treating  a  Galician  kerosene  with  sulfuric  acid, 
98.94%  H2S04,  in  the  proportions  of  50  grams  per  liter  of  oil. 

Acidity  of  Color  in  mm. 

Acid  Tar  Unused  Sulfonic  Acids  Kerosene  as  to  Match 

Temp.°C         Grams.  HzSO*  Calc.asHzSOt  H2SO*  Standard 

0                  61.6  47.91  1.45  0.86  193. 

5                  62.0  46.82  1.55  1.42  166. 

10                  62.5  46.53  1.65  1.56  143. 

15                  63.5  45.72  1.93  1.76  112. 

20                  64.3  44.37  2.22  2.45  89. 

25                  64.8  43.52  2.68  2.63  80. 

30                  65.2  41.87  3.72  3.65  52. 

40                  66.0  39.03  5.62  4.83  yellow 

50                  67.0  37.26  4.81  5.91  yellow 

Similar  results  have  been  noted  by  others.  Mechanical  agitation 
during  the  sulfuric  acid  treatment  results  in  slightly  lighter  colored 
oils  than  when  agitated  by  air.  Generally,  in  practice,  little  attention 
is  paid  to  temperature  during  the  sulfuric  acid  treatment,  particularly 
since  cooling  greatly  increases  the  viscosity  of  oils  of  the  lubricating 
class,  and  thus  greatly  prolongs  the  time  required  for  the  separation  of 
the  emulsified  acid  tar  or  sludge. 

Various  mechanical  means  have  been  tried  in  the  effort  to  increase 
the  fineness  of  the  emulsified  oil  particles,  and  also  to  decrease  the 
time  required  for  the  tar  laden  acid  to  settle  out.  For  the  latter  pur- 
pose centrifugal  separation,  and  the  addition  of  fine  sand,  infusorial 
earth  and  the  like  have  been  tried  and  while  these  methods  give  some- 
what better  oils,  these  methods  have  not  been  adopted  in  large  scale 
practice. 

Nitric  acid  or  oxides  of  nitrogen  in  the  sulfuric  acid  even  in  very 
small  percentages,157  e.  g.,  .05  to  0.10  per  cent,  results  in  darker  colored 
refined  oils.  Sulfuric  acid  made  by  the  contact  process  is,  therefore, 
much  to  be  preferred  to  chamber  acid,  aside  from  the  fact  that  the 
former  acid  is  preferable  on  account  of  its  greater  concentration. 

The  higher  boiling  distillates,  for  example,  lubricating  oils,  require 
very  much  more  acid  for  refining  than  kerosene  or  gasoline.  The 
chemical  reactions  involved  are  fairly  well  known  in  the  latter  case  but 
the  chemical  character  of  the  substances  removed  from  lubricating 


Ztff'  *v<*  V1,129-  For  data  on  the  rise  in  temperature  on  refining  oils  of 
(1908K  8ee  Kissling'  Ch&m"  Zt9-  29>  1086   <1905>  ;  Wischin,  Petroleum  3,  1062 

lwSchulz,  Ohem.  Rev.  Fett  u.  Hwz.  Ind.  20,  82  (1913). 


THE  PARAFF1NE  HYDROCARBONS  109 

oils  and  why  they  react  at  all  with  sulfuric  acid  is  not  known.  It 
is  also  possible  that  the  large  losses  thus  incurred  are  not  necessary, 
that  the  per  cent  of  substances  present  which  are  actually  objection- 
able, malodorous  substances,  easily  oxidized,  color  or  acid  forming 
substances,  is  really  very  small,  as  in  the  case  of  the  lighter  distillates. 
Naturally  many  other  reagents  have  been  tried,  including  benzensul- 
fonic  acid,  phosphoric  acid,  zinc  chloride,  aluminum  chloride  and  the 
like.  The  latter,  anhydrous  aluminum  chloride,  is  the  only  chemical 
refining  agent  other  than  sulfuric  acid,  which  has  shown  great  promise. 
The  tar  losses  in  this  case  are  very  high,  but  the  quality  of  the  prod- 
ucts produced,  gasoline,  lubricating  oil  or  white  medicinal  oil,  is  re- 
markably fine. 

Anhydrous  aluminum  chloride  polymerizes  olefines  energetically, 
decomposes  sulfur  derivatives  and  naphthenic  acids.  Color  is  very 
effectively  removed.  The  oils  so  refined  are  extremely  stable  as  regards 
oxidation  by  air.  Interest  in  this  reagent  for  refining  has  recently  been 
revived  by  McAfee158  and  Grey.159  In  polymerizing  amylenes  by 
aluminum  chloride  Aschan  obtained  a  series  of  saturated  hydrocarbons 
and  believed  methylcyclobutane,  cyclohexane  and  other  cyclic  hydro- 
carbons to  be  present  in  the  lower  boiling  fractions. 

Liquid  sulfur  dioxide  has  been  employed  to  some  extent  for  refining 
kerosene,  this  method  being  based  upon  the  marked  difference  in  solu- 
bility of  saturated  and  unsaturated  and  aromatic  hydrocarbons  in  this 
solvent.  With  many  oils  the  liquid  sulfur  dioxide  method  does  not 
yield  water  white  oils,  and  in  such  cases,  refining  with  small  proportions 
of  sulfuric  acid  must  be  resorted  to  in  order  to  get  this  result.  The 
separation  of  the  unsaturated  and  aromatic  hydrocarbons  from  the 
paraffines  is  much  more  efficient  at  low  temperatures,  a  temperature  of 
- 12°  being  recommended.160  While  it  is  a  fact  that  the  removal  of 
unsaturated  and  aromatic  hydrocarbons  improves  the  burning  quali- 
ties of  kerosene,  and  the  Edeleanu  process  can,  therefore,  be  considered 
as  a  rational  method  in  this  respect,  there  is  nothing  to  indicate  the 
refining  value  of  the  liquid  sulfur  dioxide  method  as  regards  naphthenic 
acids,  malodorous  sulfur  compounds  and  the  like.  The  method  seems 
to  be  predicated  mainly  on  the  idea  that  unsaturated  hydrocarbons 
should  be  removed  from  oils  to  be  used  as  motor  fuel,  gasoline  or 
naphtha  solvents,  lubricating  oils,  etc.  On  the  other  hand,  there  is  con- 

158  U.   S.  Pat.  1,277,328;   1,277,092;   1,277,329. 

Pat.  T.322  *878*\  SZ21GJ2** ''   1>193'541    (essentially  cracking  processes).     Cobb,  U.   8. 
16°'See'  section   on   Physical   Properties ;    Solubility. 


110      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

siderable  evidence  indicating  that  it  is  possible  to  refine  motor  fuel  and 
lubricating  oils  to  a  satisfactory  degree  without  the  large  losses  at- 
tendant upon  the  removal  of  the  unsaturated  hydrocarbons  and  aro- 
matic hydrocarbons.  That  benzene  can  be  satisfactorily  used  as  a  mo- 
tor fuel,  particularly  when  mixed  with  gasoline,  or  gasoline  and  alcohol 
is  now  generally  recognized.  It  is  probable  that  the  unsaturated 
hydrocarbons  themselves,  as  removed  from  pyrolytic  process  motor 
fuel  by  the  Edeleanu  method,  can  be  employed  successfully  in  internal 
combustion  engines,  provided  the  resin  forming  conjugated  diolefines, 
present  only  in  very  small  proportions,  be  removed  by  fuller's  earth 
according  to  Hall's  refining  process,  or  an  equivalent  method.161  It  is 
also  probable  that  transformer  oils  and  oils  intended  for  the  lubricat- 
ing of  air  compressors  and  internal  combustion  engines  should  be  free 
from  unsaturated  hydrocarbons  on  account  of  the  general  tendency  of 
such  hydrocarbons  to  be  readily  oxidized  by  air.  But  it  is  possible 
that  highly  unsaturated  but  otherwise  refined  oils  would  prove  satis- 
factory even  in  these  instances.  Considerable  research  needs  to  be 
carried  out  in  order  to  determine  precisely  in  what  refining  for  par- 
ticular purposes  should  consist,  and  to  develop  industrially  feasible 
methods  of  refining,  which  would  remove  the  objectionable  constituents 
with  little  or  no  loss  of  the  valuable  hydrocarbons. 

lei  The  writer  has  seen  test  runs  of  an  automobile  engine  in  which  pure  turpen- 
tine was  used  as  the  fuel,  without  abnormal  deposition  of  carbon,  with  excellent 
thermal  efficiency  and  without  carburetor  difficulties.  A  great  many  of  our  ideas  as  to 
what  the  characteristics  of  good  motor  fuel  should  be  have  apparently  been  derived 
from  the  commercial  salesman,  who  had  a  certain  article  to  sell. 


Chapter  IV.     The  Ethylene  Bond 

Theory  of  the  Ethylene  Bond  and  Cyclic  Structures 

It  is  probably  not  exaggerating  the  relative  importance  of  the  mat- 
ter to  state  that  the  chemical  behavior  and  physical  properties  of  the 
unsaturated  olefine,  or  ethylene  group,  is  fully  as  important  as  the 
well  differentiated  properties  of  condensed  or  benzenoid  structures. 
The  chemical  properties  of  the  ethylene  structure  cannot  properly  be 
indicated  by  a  few  so-called  type  reactions  and  in  the  following  dis- 
cussion it  will  be  pointed  out  that  all  of  the  important  chemical  prop- 
erties of  this  group  may  be  greatly  influenced  by  structural  configura- 
tion and  proximity  of  other  groups  or  substituents.  The  properties  of 
this  group  as  displayed  in  the  enol  form  of  tautomeric  compounds  is 
not  discussed  at  length  as  this  material  has  been  well  presented  else- 
where and  it  is  moreover  not  strictly  germane  to  the  subject  of  hydro- 
carbon chemistry. 

It  will  be  of  interest  to  examine  the  current  theories  regarding  the 
atomic  structure  of  such  a  linking.  That  the  group  >C  =  C<  is  rela- 
tively unstable,  or  under  stress  (Baeyer),  is  indicated  by  a  wealth  of 
experimental  evidence.  Our  conceptions  or  theories  of  such  carbon 
"linkings"  have  been  greatly  advanced  by  the  general  hypotheses  re- 
cently published  by  Lewis  and  by  Langmuir.  First,  Lewis  l  pointed 
out  that  "a  study  of  the  mathematical  theory  of  the  electron  leads,  I 
believe  (irresistibly  to  the  conclusion  that  Coulomb's  law  of  inverse 
squares  must  fail  at  small  distances."  Like  Parson,2  Lewis  believed 
that  the  most  stable  condition  for  the  atomic  shell  is  the  one  in  which 
eight  electrons  are  held  at  the  corners  of  a  cube.  As  regards  the  carbon 
atom  Lewis  may  again  be  quoted.  "Assuming  now,  at  least  in  such 
very  small  atoms  as  that  of  carbon,  that  each  pair  of  electrons  has  a 
tendency  to  be  drawn  together,  perhaps  by  magnetic  force  if  the  mag- 
netic theory  (of  Parson)  is  correct,  or  perhaps  by  other  forces  which 
become  appreciable  at  small  distances,  to  occupy  positions  indicated 
by  the  dotted  circles,  we  then  have  a  model  which  is  admirably  suited 
to  portray  all  of  the  characteristics  of  the  carbon  atom.  With  the 

1J.  Am.   Gliem.  Soc.  38,  773    (1916). 
'Smithsonian  Inst.  Public  65,  1915,  p.  2371. 

Ill 


112      CHEMISTRY  OF  THE  NON-BEN  ZEN01D  HYDROCARBONS 

cubical  structure  it  is  not  only  impossible  to  represent  the  triple  bond, 
but  also  to  explain  the  phenomena  of  free  mobility  about  a  single  bond 
which  must  always  be  assumed  in  stereochemistry.  On  the  other  hand, 
the  group  of  eight  electrons  in  which  the  pairs  are  symmetrically  placed 
about  the  center  gives  identically  the  model  of  the  tetrahedral  car- 
bon atom  which  has  been  of  such  utility  throughout  the  whole  of  or- 
ganic chemistry."  Then  two  such  tetrahedra,  attached  by  one,  two  or 
three  corners  of  each,  represent  respectively  the  single,  double  and 
triple  bond.  In  the  first  case,  one  pair  of  electrons  is  held  in  common 
by  the  two  atoms;  in  the  second  case  two  such  pairs  and  in  the  third 
case,  three  such  pairs. 

According  to  Lewis,  the  triple  bond  represents  the  highest  possible 
degree  of  union  between  two  atoms.  Like  a  double  bond  it  may  break 
one  bond  producing  two  odd  carbon  atoms,  but  it  may  also  break  in  a 
way  in  which  the  double  bond  cannot,  i.  e.,  to  leave  a  single  bond  and 
two  carbon  atoms  (bivalent),  each  of  which  has  a  pair  of  electrons 
which  is  not  bound  to  any  other  atom.  The  three  resulting  structures, 
in  the  case  of  acetylene,  may  be  represented  as  follows,  H :  C : : :  C :  H, 
H  :  C  :  :  C  :  H  and  H  :  C  :  C  :  H.  In  addition  we  have  a  form  cor- 
responding to  Nef 's  acetylidene  and  such  forms  as  may  exist  in  highly 
polar  media,  such  as  the  acetylidene  ion  :  C  :  :  :  C  :  H. 

The  instability  of  multiple  bonds,  as  well  as  the  general  phenome- 
non of  ring  formation  in  organic  compounds,  is  admirably  interpreted 
by  the  Strain  Theory  of  Baeyer.  This  theory  may,  however,  be  put 
into  a  far  more  general  form  if  we  make  the  simple  assumption  that 
all  atomic  kernels  repel  one  another,  and  that  molecules  are  held  to- 
gether only  by  the  pairs  of  electrons  which  are  held  jointly  by  the 
component  atoms.  Thus  two  carbon  atoms  with  a  single  bond  strive 
to  keep  their  kernels  as  far  apart  as  possible,  and  this  condition  is  met 
when  the  adjoining  corners  of  the  two  tetrahedra  lie  in  the  line  joining 
the  centers  of  the  tetrahedra.  This  is  an  essential  element  of  Baeyer's 
Theory  of  stress  in  cyclic  structures.  When  a  single  bond  changes  to  a 
multiple  bond  and  the  two  atomic  shells  have  two  pairs  of  electrons 
in  common,  the  kernels  are  forced  nearer  together  and  the  mutual  re- 
pulsion of  these  kernels  greatly  weakens  the  constraints  at  the  points 
of  junction.  This  diminution  in  constraint,  therefore,  produces  a  re- 
markable effect  in  increasing  the  mobility  of  the  electrons.  In  any 
part  of  a  carbon  chain  where  a  number  of  consecutive  atoms  are  dou- 
bly bound  there  is  in  that  whole  portion  of  the  molecule  an  extraor- 


THE  ETHYLENE  BOND  113 

dinary  reactivity  and  freedom  of  rearrangement.  This  freedom  usu- 
ally terminates  at  that  point  in  the  chain  where  an  atom  has  only 
single  bonds  and  in  which,  therefore,  the  electrons  are  held  by  more 
rigid  constraints,  although  it  must  be  observed  that  an  increased  mo- 
bility of  electrons  (and  therefore  increased  polarity)  in  one  part  of 
the  molecule  always  produces  some  increase  in  mobility  in  the  neigh- 
boring parts. 

"There  is  much  chemical  evidence,  especially  in  the  field  of  stereo- 
chemistry, that  the  primary  valence  forces  between  atoms  act  in  di- 
rections nearly  fixed  with  respect  to  each  other."  3 

"Further  evidence  for  the  stationary  electrons  has  been  obtained 
by  Hull,  who  finds  that  the  intensities  of  the  lines  in  the  X-ray  spectra 
of  crystals  are  best  accounted  for  on  the  theory  that  the  electrons 
occupy  definite  positions  in  the  crystal  lattice." 

According  to  Langmuir's  postulates  carbon,  atomic  number  six,  has 
normally  six  electrons,  two  situated  close  to  the  nucleus  or  kernel  as 
in  helium,  and  the  "four  electrons  in  the  second  shell  tend  to  arrange 
themselves  at  the  corners  of  a  tetrahedron  for  in  this  way  they  can  get 
as  far  apart  as  possible."  Langmuir  regards  the  electrons  in  the  atoms 
"as  able  to  move  from  their  normal  positions  under  the  influence  of 
magnetic  and  electrostatic  forces." 

It  should  be  borne  in  mind  when  reviewing  the  chemical  properties 
of  the  ethylene  bond  that  there  is  no  set  of  reactions  which  infallibly 
characterize  this  group  as  distinguished  from  other  unsaturated  types, 
particularly  cyclopropane  derivatives.  This  is  in  accord  with  Baeyer's 
strain  theory  and  it  is  probably  worth  while  to  emphasize  these  rela- 
tionships and  briefly  review  the  theory. 

Baeyer  was  much  impressed  by  the  explosibility  of  the  poly  acety- 
lene compounds  and  endeavored  to  visualize  the  manner  in  which  en- 
ergy could  be  absorbed  in  the  formation  of  the  acetylene  bond,  this 
energy  being  released  as  heat  when  such  a  substance  explodes..  From 
the  generalization  of  van't  Hoff  and  LeBel,  Baeyer  inferred  that  "the 
four  valences  of  the  carbon  atom  act  in  directions  which  connect  the 
center  of  the  sphere  with  the  corners  of  a  (inscribed)  tetrahedron,  and 
which  form  an  angle  of  109°  28'  with  each  other.  The  direction  of  the 
attraction  (or  valence)  can  undergo  a  bending  or  distortion,  which  re- 
sults in  a  tension  (Spannung)  proportional  to  the  amount  of  this  bend- 


ing." 4 


'Langmuir,  J.  Am.  CTiem.  Soc.  &,  686    (1919). 
*Ber.  18,  2269    (1885). 


114      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

"Ethylene  is  the  simplest  methylene  ring,  as  it  may  be  regarded  as 
dmiethylene."  In  order  to  bend  two  of  these  hypothetical  lines  of 
valence  direction  to  parallel  positions  would  require  that  each  of  the 
pair  be  deviated  one-half  109°  28'  or  54°  44'  from  their  normal  direc- 
tions. In  the  same  way  the  supposed  deviations  from  the  normal  va- 
lence direction  may  be  calculated  for  cyclopropane,  cyclobutane,  and 
so  on.  Ring  structures  containing  more  than  five  carbon  atpms  would 
require  a  spreading  or  widening  of  the  normal  angle,  the  angles  of  devi- 
ation of  the  simpler  cyclic  carbon  structures  being  as  follows: 

CH2  CH2  CH2  — CH2  CH2  — CH2 

II  I      >CH2  |  |  |  >CH2 

OTJ  OTI  OTT  O~H 

L>±12  v^-tl-2  v^±i2  —  ^-n_ 

_j_  540  44'       _|_  24°  44'  +  9°  44'  0°  +  44 

H2 
H2  C 

C 

H2C  CH2  H2C  CH2 

H2C  CH2  H2C  CH2 

V  \      / 

vv  vy  ~        \j 

H2  H2    H2 

—  5°  16'  -9°  33' 

cyclooctane,  — 12°  46' 
cyclononane,  —  15°  16' 

Cyclopropane  and  its  derivatives  are  generally  not  as  reactive  as 
ethylene  but  the  ring  is  broken  by  bromine,  hydriodic  acid,  and  by 
hydrogen  in  contact  with  nickel  at  80°.  Cyclopropane  is  not  oxidized 
by  cold  dilute  permanganate.  Cyclobutane  is  not  reacted  upon  by 
bromine*  concentrated  hydroiodic  acid  or  dilute  permanganate  solution. 
The  ring  is  opened  by  hydrogen  in  the  presence  of  nickel,  forming 
butane  at  high  temperature  but  is  stable  at  100°.  The  stability  of 
cyclopropane  and  cyclobutane  rings  toward  oxidizing  agents,  bromine, 
halogen  acids,  dilute  sulfuric  acid  and  the  like  is  very  greatly  modified 
by  substituent  groups,  just  as  the  chemical  behavior  of  the  ethylenes 
is  altered  by  different  groups.  Thus  1 . 2-dimethylcyclopropane  is  acted 
upon  by  1%  permanganate5  and  the  hydrocarbon  1, 1, 2-trimethyl 

•Zelinsky,  J.  prakt.   Chem.  84,  II,  543    (1911). 


THE  ETHYLENE  BOND  115 

cyclopropane  combines  with  concentrated  hydrochloric  acid  at  100°. 
The  derivatives 

CMe2  CMe2 

CH2<  I  and  CH2<  | 

CH .  CH2CHMe2  CH .  C02H 

are  stable  to  permanganate  solution  but  the  former  is  hydrogenated 
in  contact  with  nickel  at  125°  and  adds  hydrobromic  acid  very  slow- 
ly.6 Ethylcyclobutane  is  extremely  stable,  being  unaffected  by  per- 
manganate solution,  concentrated  hydrobromic  acid  at  100°,  concen- 
trated sulfuric  acid  at  25°  and  is  only  reduced  by  HI  at  210°. 

The  cyclobutane  derivative  1, 1, 3, 3-tetramethyl  2, 4-diethylcyclo- 
butane 

Me2C CHC2H5 

C2H5CH  —  CMe2 

is  also  remarkable  for  its  stability,  its  chemical  behavior  resembling 
that  of  a  saturated  hydrocarbon  of  great  inertness.7  The  acid  chloride 

CH2 

>CHCOC1  is  sufficiently  stable  to  anhydrous  aluminum  chloride 
CH2 

and  hydrogen  chloride 8  to  react  normally  in  the  Friedel  and  Crafts 

CH2 

synthesis  to  give  good  yields  of  the  ketone  C6H5OC.CH<  |      .    This 

CH2 

fact  is  somewhat  remarkable  in  view  of  the  ease  with  which  the  cyclo- 
propane ring  in  carane  and  sabinene  arid  the  cyclobutane  ring  in 
the  pinenes  is  ruptured  by  halogen  acids,  by  bromine  and  by  di- 
lute mineral  acids.  Wallach 9  has  noted  that  the  ketonic  acid 

CH.COCH,  CH.C02H 

CH2<  I  is  very  unstable,  but  the  acid  CH2<  | 

C  — CH2C02H  *  C  — CH2C02H 

C3H7  C3H7 

is  very  stable. 

Although  Baeyer's  theory  needs  revision  in  the  light  of  our  present 
knowledge  and  theories  of  valence  and  atomic  structure,  it  has  passed 

•Kishner,  J.  Chem.  Soc.  Aba.  1913,  I,  1163. 
'Wedekind  &  Miller,  Ber.  kk,  3285   (1911). 
•Kishner,  J.  Russ.  Phys.-Cliem.  Soc.  tf,  1163  (1911). 
•Ann.  360,  82    (1908)  ;  388,  49   (1912). 


116      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

the  test  of  usefulness  and  been  of  very  great  value.  Experience  is  gen- 
erally in  accord  with  the  theory  and  the  yields  in  analogous  reactions 
of  synthesis  indicate  that  in  the  cyclopropane,  cyclobutane,  cyclopen- 
tane  and  cyclohexane  series,  derivatives  of  cyclopropane  are  produced 
with  the  greatest  difficulty  or  poorest  yields,  and  that  while  cyclobu- 
tane and  cyclohexane  derivatives  are  much  more  easily  obtained,  the 
tendency  to  form  cyclopentane  derivatives  is  so  pronounced  that  quan- 
titative yields  are  frequently  produced  and,  in  fact,  cyclopentane  de- 
rivatives sometimes  result  during  reactions  which  might  be  expected 
to  yield  other  ring  structures.  As  regards  the  relative  influence  of 
different  substituent  groups  in  such  syntheses  Perkin  10  states  that  it 
is  clear  that  a  useful  generalization  cannot  be  formulated  until  a  much 
larger  number  of  cyclic  carboxylic  acids  and  other  derivatives  have 
been  prepared  and  investigated.  J.  von  Braun xl  states  that  1,4  di- 
halogen  alkyls  and  sodium  malonic  ester  give  good  yields  of  cyclo- 
pentane derivatives  but  the  same  reaction  applied  to  the  synthesis  of 
cyclohexane  and  cycloheptane  compounds,  from  the  1, 5  and  1, 6  di- 
halogen  derivatives,  respectively,  give  very  poor  yields.  The  ease  with 
which  cyclohexanones  are  converted  to  cyclopentanones  has  been 
noted  by  Wallach 12  and  the  four  carbon  ring  in  cyclobutyldiethyl- 
carbinol,  on  decomposition  with  loss  of  water,  forms  the  five  carbon 
ring  1, 2-diethylcyclopentene.13  However,  a  very  large  number  of  re- 
arrangements have  been  observed  in  which  'change  to  a  system,  less 
stable  so  far  as  the  Baeyer  theory  and  the  number  of  carbon  atoms  in 
the  ring  is  concerned,  is  brought  about.14 

J.  F.  Thorpe  15  and  his  assistants  reasoned  that  if  two  valences  of 
a  given  carbon  atom  are  under  strain  due  to  ring  formation,  the  di- 
rections of  the  two  remaining  valences  would  be  affected,  for  example, 
the  angle  formed  by  two  side  chains  attached  to  a  carbon  atom  in  a 
ring  such  as  cyclohexane,  would  be  bent  from  the  normal  109°  28'  re- 
quired by  Baeyer's  theory.  In  the  case  of  cyclohexane  these  two  side 
chains  may  be  closer  together  than  in  a  corresponding  compound  hav- 
ing an  open  chain  structure.  Their  results  are  an  interesting  confirma- 
tion of  the  theory.  Thorpe  has  compared  the  relative  stability  of 
the  cyclopropane  derivatives  formed  by  the  elimination  of  hydrogen 

10  Cf.  Goldsworthy  &  Perkin,  J.  Chem.  Soc.  105,  2665    (1914). 

12  J.  Chem.  Soc.  Abs.  1916,  I,  487. 

13  Kishner,  Chem.  Zentr.  1912,  I,  1001. 

14  See  chapter  on  Rearrangements. 

"Beesley,  Ingold  &  Thorpe,  J.  Chem.  Soc.  107,  1080   (1915) 


THE  ETHYLENE  BOND  117 

bromide  from  the  monobromo  derivatives  of  cyclohexane-1  .  1-diacetic 
acid  and  P|3-dimethylglutaric  acid,  as  follows, 

CH2CH2  CHBr.C02H 

CH2<  >C<  _* 

CH2CH2  CH2C02H. 

CH2CH2  CH.C02H 


CH2<  >C<  | 

CH2CH2          CH.C02H 

CH3  CHBr.C02H.          CH3  CH.C02H 


CH3  CH2C02H.  CH3  CH.C02H. 

Both  of  the  resulting  acids  are  remarkably  stable  towards  boiling  acid 
permanganate  solution  but  the  chief  difference  observed  was  in  their 
behavior  to  concentrated  hydrochloric  acid  in  sealed  tubes  at  240° 
under  which  conditions  the  spiro  acid,  from  cyclohexanediacetic  acid, 
is  unaffected  but  the  other,  trans-caronic  acid,  is  completely  changed 
to  terebic  acid,  with  rupture  of  the  ring. 

The  thermal  measurements  of  Stohmann  and  Kleber  are  not  in 
good  agreement  with  Baeyer's  theory.  According  to  their  work,  the 
quantities  of  heat  absorbed  in  the  formation  of  similarly  constituted 
compounds  containing  the  cyclopropane,  cyclobutane,  cyclopentane 
and  cyclohexane  rings  by  the  removal  of  two  atoms  of  hydrogen  from 
the  corresponding  open-chain  substances,  are  as  follows: 

Ring  .............................     C8  C4  C6  C, 

Angle  of  strain  (Baeyer)  ..........     24.7°  9.7°  0.7°  5.3° 

Heat  absorbed,  calories  ...........     38.1  42.6  16.1  '  14.3 

Ingold  16  has  suggested  that  these  calculated  angles  of  strain  may 
not  be  correct  and  that  the  normal  tetrahedral  angle  of  Baeyer 
(2  tan-1  V  2  =  109.5°)  may  be  modified  somewhat  according  to  the 
volume  occupied  by  the  four  attached  atoms  or  groups.  (The  distor- 
tion of  the  valency  direction,  as  suggested  by  Ingold,  has  nothing  in 
common  with  the  theories  of  Guye  and  Brown,  which  refer  to  the  ef- 
fect of  the  size  of  the  substituent  radicles  upon  the  asymmetry  of  the 
molecule  as  measured  by  the  molecular  optical  activity.) 

Ingold  suggests  that  "the  tetrahedron  representing  a  carbon  atom 
is  approximately  regular  only  when  the  carbon  atom  is  attached  to 
four  atoms  of  a  similar  kind,"  for  example,  to  four  carbon  atoms, 

M  J.  Chem.  Soc.  119,  306   (1921). 


118      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

(A)  .    However  in  cyclopropane,  cyclobutane  and  the  like,  each  carbon 
atom  is  attached  to  two  hydrogen  atoms  and  two  carbon  atoms,  (B). 

C          C  H          C 

v         v 

/  \  H/  \ 

(A)  (B) 


Since  the  hydrogen  atom  occupies  a  much  smaller  volume  than  the  car- 
bon atom,  it  is  accordingly  possible  that  in  the  >CH2  group  the  two 
carbon  atoms  attached  to  the  central  one  occupy  more  of  the  sur- 
rounding space  than  do  the  hydrogen  atoms.  If  this  is  so,  the  angle  be- 
tween the  carbon-to-carbon  valencies  of  a  polymethylene  chain  will 
not  be  109.5°,  as  hitherto  supposed,  but  will  be  some  angle  greater 
than  this."  Using  Traubes  values  for  the  atomic  volumes  of  carbon 
and  hydrogen,  Ingold  calculates  that  this  volume  factor  causes  a 
change  in  the  angles  between  each  pair  of  carbon-to-carbon  valencies 
in  a  polymethylene  chain  and  that  this  angle  may  be  nearly  6°  greater 
than  has  hitherto  been  supposed.  Employing  this  new  angle  115.3° 
instead  of  109.5°,  Ingold  calculates  "by  how  much"  the  terminal  car- 
bon atoms  of  C3,  C4,  C5,  and  C6  rings  must  approach  one  another  and 
obtains  values  more  nearly  in  accord  with  the  thermal  results  of  Stoh- 
mann  and  Kleber. 

The  above  stereo-chemical  considerations  afford  an  explanation  of 
the  effect  of  the  gem-dimethyl  group  in  promoting  certain  reactions 
and  in  other  cases  greatly  increasing  the  stability  of  the  substance. 
Thus,  cux-dimethylbutane  -apy-tricarboxylic  acid  is  smoothly  con- 
verted into  the  cyclopentanone  derivative,  on  heating  its  sodium  salt 
with  acetic  anhydride,  but  this  change  has  not  been  observed  with 
adipic  acids  which  do  not  contain  a  gem-dimethyl  group.  The 
(CH3)2C<  group  stabilizes  certain  lactones,  for  example,  |3p-dimeth- 
ylglutaric  anhydride  may  be  boiled  in  water  for  hours  without  change, 
and  a|3|3-trimethylglutaric  anhydride  may  be  crystallized  from  hot 
water  in  crystals  containing  water  of  crystallization,  but  ordinary  glu- 
taric  anhydride  is  easily  decomposed  by  water. 

Hiickel  17  regards  the  heat  of  combustion  of  CH2  as  different  in 
each  polymethylene  ring  and  points  out  that  if  the  heats  of  combustion 
of  these  hydrocarbons  are  divided  by  the  number  of  CH2  groups 

^er.  53  B,  1277  (1920). 


THE  ETHYLENE  BOND  119 

tained  in  the  hydrocarbon  concerned,  then  values  are  obtained  which 
are  much  better  in  accord  with  Baeyer's  theory  than  the  older  com- 
parisons of  Stohmann.  In  this  way,  the  values  for  CH2  in  ethylene, 
cyclopropane,  cyclobutane,  cyclopentane  and  cyclohexane  are  calcu- 
lated to  be  170,  168.5,  165.5,  159,  158  calories,  respectively. 

In  view  of  the  fact  that  the  chemical  behavior  of  the  cyclopropane 
group  reveals  a  condition  of  unsaturation  or  strain  (Baeyer)  it  is  not 
surprising  that  ring  closing  in  this  case  influences  the  physical  proper- 
ties of  substances  containing  this  ring  complex.  This  will  be  discussed 
more  fully  in  the  section  dealing  with  physical  properties  and  constitu- 
tion but  it  may  be  noted  here  that  one  of  the  most  significant  and  use- 
ful properties,  refractivity,  is  affected  by  the  formation  of  the  3  carbon 
ring  to  almost  the  same  degree  as  in  the  case  of  the  ethylene  bond, 
and  that  when  the  cyclopropane  group  occurs  in  a  conjugated  position 
to  an  ethylene  bond  substantially  the  same  degree  of  exaltation  is  ob- 
served as  is  noticed  in  the  case  of  two  conjugated  ethylene  bonds. 


Chemical  Properties  of  Unsaturated  Substances  of  the  Ethylene 

Type. 

Unsaturated  substances  of  the  ethylene  type,  e.  g.,  substances  con- 
taining one  or  more  so-called  olefine  groups,  are  capable  of  a  series 
of  reactions  which  are  very  widely  applicable  to  nearly  all  substances 
containing  such  an  Unsaturated  group  and  which  have  come  to  be  re- 
garded as  characteristic  reactions  of  this  type  of  unsaturation.  These 
reactions  are  best  exemplified  by  the  addition  of  ozone,  of  halogens, 
particularly  bromine,  oxidation  by  potassium  permanganate  solution 
to  the  corresponding  glycols,  addition  of  nitrosyl  chloride  and  oxides 
of  nitrogen.  Other  reactions  less  widely  applicable  will  be  noted  be- 
low. All  of  these  reactions  involve  rupture  of  one  of  the  ethylenic 
linkings  or,  in  other  words,  one  of  the  primary  valences.  In  addition 
to  these  reactions,  it  has  been  noted  that  substituted  ethylenes  are 
capable  of  forming  a  large  number  of  so-called  molecular  compounds 
with  other  substances.  In  these  compounds  the  double  bond  is  not 
broken  and  the  formation  of  these  molecular  compounds  is  due  to  what 
is  termed,  for  lack  of  a  better  name,  "residual  valence,"  "latent  affin- 
ity," "secondary  valence,"  and  similar  terms.'  It  should  be  pointed  out, 
however,  that  the  ability  to  form  such  molecular  compounds  is  by  no 
means  limited  to  Unsaturated  substances  of  the  ethylene  type. 


120      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

Well  crystallized  compounds  of  p-tetrabromotetraphenylethylene 
with  acetone,  ether,  methylethyl  ketone,  carbon  tetrachloride,  ethyl 
acetate  and  benzene,  have  been  described.  These  compounds  are  easily 
decomposed  to  the  original  constituent  substances.  Norris  18  has  sub- 
mitted the  following  hypothesis  in  regard  to  substances  of  this  kind. 

(1).  The  molecular  compound  is  formed  as  a  result  of  the  com- 
ing into  play  of  latent  affinities  residing  in  an  atom  in  each  of  the 
constituents  of  the  compound. 

(2).  All  atoms  possess  these  latent  affinities.  If  an  atom  in  a 
compound  reacts  with  difficulty  when  the  latter  is  brought  into  con- 
tact with  other  substances,  it  is  evident  that  a  large  part  of  its  energy 
has  been  expended  and  but  a  little  of  it  remains  to  take  part  in  re- 
action. On  the  other  hand,  if  the  atom  enters  into  reaction  readily  with 
other  substances,  it  is  evident  that  it  still  possesses  available  energy. 
It  is  probable,  therefore,  that  such  active  atoms  might  be  able  to  unite 
with  atoms  of  a  similar  nature  (with  respect  to  residual  energy)  and 
form  molecular  compounds.  A  study  of  the  literature  confirms  the 
view  that  compounds  containing  unusually  active  elements  or  groups 
form  well  characterized  molecular  compounds. 

(3).  Substances  which  contain  inactive  double  bonds  may  form 
molecular  compounds.  In  most  cases  direct  addition  of  atoms  or 
groups  at  the  double  bond  leads  to  the  formation  of  ordinary  saturated 
compounds.  So-called  unsaturated  compounds  are  known,  however, 
in  which  the  unsaturation  is  so  slight  that  they  will  not  unite  with  such 
an  active  element  as  bromine.  The  chemical  affinity  latent  in  the  dou- 
ble bond  is  so  small  that  it  cannot  hold  in  combination  other  atoms 
or  groups  linked  to  it  by  primary  valence  bonds.  Many  such  com- 
pounds form  well  characterized  molecular  compounds.  In  other  words, 
the  available  energy  of  the  double  bond  is  not  enough  to  neutralize 
the  energy  of  atoms  and  form  a  true  valence  bond,  but  is  suf- 
ficient to  interact  with  a  similar  small  amount  of  energy  residing  in 
another  compound.  For  example,  p-tetrabromotetraphenylethylene 
(BrC6HJ2C  =  C(C6H4Br)2  will  not  react  with  bromine,  as  shown  by 
Bauer,19  but  it  does  form  a  series  of  molecular  compounds,  as  noted 
above.  [There  is  apparently  no  way  of  determining  whether  the  resid- 
ual energy  which  makes  these  combinations  possible  in  this  case  is 
really  inherent  in  the  double  bond  or  in  the  bromine  atom.  The  latter 
possibility  suggests  itself  in  view  of  the  fact  that  tetraphenylethylene 

18  J.  Am.  Ohem.  Soc.  ft,  2086   (1920). 

"Ber.  37,  3317  (1904)  ;  Hinrichsen,  Ann.  336,  223   (1904). 


THE  ETHYLENE  BOND  121 

dichloride  (C6H5)2CC1.CC1(C6H5)2  also  forms  molecular  compounds. 
B.  T.  B.] 

The  hypothesis  that  unsaturated  hydrocarbons  are  able  to  unite 
with  acids,  by  virtue  of  "free  partial  valences,"  to  form  salt-like  sub- 
stances was  put  forward  and  subsequently  rejected  by  Baeyer  but 
Kehrmann  and  Effront 20  have  revived  the  hypothesis  to  account  for 
the  formation  of  two  series  of  salts  by  the  triphenyl  methane  dyes,  and 
for  the  behavior  of  certain  unsaturated  ketones  towards  acids.  For  ex- 
ample, distyryl  ketone  gives  mono-  and  di-acid  compounds,  lemon- 
yellow  and  orange-red  respectively,  from  which  it  seems  necessary  to 
assume  that  combination  can  occur  at  one  double  bond  in  addition 
to  the  oxygen  atom. 

The  reaction  of  bromine  with  styrene  and  substituted  styrenes 
shows  that  replacement  of  one  of  the  methylenic  hydrogen  atoms  by 
an  aryl  group  increases  the  reactivity  to  bromine  slightly  and  this 
difference  is  further  accentuated  by  substituting  both  hydrogen  atoms 
by  alkyl  groups.  The  introduction  of  one  halogen  atom  decreases  the 
reactivity  toward  bromine  but  the  effect  of  a  CN  group  is  even  more 
marked,  the  effect  of  the  CN  and  carboxyl  group  being  of  about  the 
same  order.21 

Double  compounds  of  ethylene  and  aluminum  chloride  have  been 
isolated  but  energetic  polymerization  occurs  with  most  olefines.  Very 
little  work  has  been  done  with  the  Friedel  and  Craft  reaction  as  ap- 
plied to  non-benzenoid  hydrocarbons.  Darzens  22  found  that  acetyl 
chloride  did  not  react  with  cyclohexane  in  the  presence  of  aluminum 
chloride  but  with  cyclohexene  the  saturated  chloro  ketone  was  formed. 

H        Cl 
X 


CH3COC1A1C13  /        \_oo.ctt 


v 

Stannic  chloride  is  a  most  efficient  catalyst  for  this  reaction.    Norris 
and  Couch23  have  recently  noted  that  ethylene  reacts  with  benzoyl 

2°Bcr.  5k,  417   (1921). 

"Reich  et  al.  Helv.  Chim.  Acta.  4,  242  (1921). 

22  Compt.  rend.  150,   707    (1910).     The  chloride  noted  above  may  be  decomposed 

by  alkali  to  give  the  unsaturated  ketone,— HC=C<COCH3 
nJ.  Am.   Chem.  Soc.  42,  2330   (1920). 


122      CHEMISTRY  OF  THE  NON-BENZEN01D  HYDROCARBONS 

chloride  in  the  presence  of  A1C13  apparently  in  a  different  manner,  to 
give  phenyl  vinyl  ketone  C6H5CO .  CH  =  CH2.  The  chloride, 
C6H5CO.CH2CH2C1,  corresponding  to  Darzen's  product,  was  not  ob- 
served. 

There  is  no  subject  in  organic  chemistry  to  which  it  is  more  diffi- 
cult to  give  accurate  expression  than  the  modification  of  the  chemical 
behavior  of  certain  groups  or  siibstituent  atoms  by  other  groups  or 
atoms  in  the  same  molecule.  As  pointed  out  by  Bauer  the  substitu- 
tion in  ethylene  of  strongly  negative  groups  diminishes  the  ability  of 
the  substance  to  react  with  bromine.24  ,0n  the  other  hand,  the  substi- 
tution of  halogens  or  the  phenyl  group  very  markedly  increases  the 
reactivity  of  the  ethylene  group  in  certain  other  respects.  Thus  ethyl- 
ene is  polymerized  only  at  high  temperatures  and  pressures  and  in 
the  presence  of  catalysts  such  as  alumina  or  iron,  or  in  the  presence  of 
very  reactive  substances  such  as  anhydrous  aluminum  chloride  or  zinc 
chloride.  On  the  other  hand,  styrene  C6H5CH  =  CH2,  vinyl  bromide, 
CH2  =  CHBr,  and  vinyl  chloride  polymerize  on  standing  at  ordinary 
temperatures,  and  rapidly  under  the  influence  of  light.  The  enhanced 
reactivity  of  the  hydrogen  atoms  in  styrene  is  also  indicated  by  the 
fact  that  this  substance  yields  the  nitro  derivative  C6H5CH  =  CHN02 
when  treated  with  nitric  acid.25 

That  the  double  bond  greatly  influences  the  reactivity  of  the  sub- 
stituent  halogen  atoms  is  also  well  known.  Thus  vinyl  bromide  and 
vinyl  chloride  are  remarkably  stable  to  alkalies  and  in  many  of  their 
reactions  closely  resemble  chloro-benzene  and  bromobenzene.  Ad- 
vantage is  taken  of  this  unusual  stability  of  chlorine  substituted  ethyl- 
enes,  with  respect  to  reactivity  of  the  chlorine,  in  utilizing  them  as 
commercial  solvents.  For  example,  trichloroethylene,  CHC1  =  CC12, 
is  not  appreciably  hydrolyzed  by  hot  water  and  is  practically  not  af- 
fected by  iron  or  copper  and  is  therefore  admirably  adapted  for  use 
as  a  solvent  in  industrial  apparatus  made  of  these  metals.26  This  sta- 
bility of  halogen  derivatives  of  ethylene  is  also  indicated  by  the  com- 
mercial methods  of  manufacturing  trichloroethylene,  e.  g.,  treating 
tetrachloroethane  with  alkali  or  passing  over  thorium  oxide  at  390°. 27 
On  treating  trichlorocyclohexane  with  alcoholic  caustic  potash  the  prin- 

24  Perkin  has  called  attention  to  the  fact  that  the  stability  of  cyclopropane  and 
cyclobutane  derivatives  is  variable  within  wide  limits  depending  upon  the  character 
of  the  substituent  groups. 

28  Recent  work  of  Wieland,  Ber.  M,  201  (1920),  shows  that  ethylene  reacts  with 
a  mixture  of  nitric  and  sulfuric  acids  (20%  oleum)  to  give  a  mixture  of  ethylene 
dinitrate  and  B-nitro-ethyl  nitrate. 

26  Gowing-Scopes,  J.  tSoc.  Chem.  Ind.  S3,  160   (1914)  ;  Crudes,  Chem.  Aba.  1917,  544. 

27  German  Pat.  171,900;  206,854   (1906)  ;  274,782   (1914). 


THE  ETHYLENR  BOND  123 

cipal  product  is  chlorodihydrobenzene,  C6H7C1,  the  last  chlorine  atom 
being  stabilized  by  the  adjacent  double  bonds. 

Wohl 28  has  shown  that  when  tetramethylethylene  (CH3)2C  = 
C(CH3)2  is  treated  with  n-bromoacetamide,  primary  addition  occurs 
through  subsidiary  valences  of  the  bromoacetamide  and  of  one  or  both 
of  the  unsaturated  carbon  atoms  of  the  olefine.  Acetamide  is  then 
formed,  the  bromine  atom  taking  the  place  of  the  hydrogen  re- 
moved to  form  acetamide,  the  final  products  being  acetamide  and 
(CH3)  2C  =  C .  CH3 .  CH2Br. 

Free  bromine  reacts  energetically  with  the  unsaturated  hydro- 
carbons and  therefore  solvents  are  •  usually  employed  in  such  re- 
actions, e.  g.,  carbon  bisulfide,  carbon  tetrachloride,  glacial  acetic 
acid  and,  less  generally,  alcohol  or  ether.  The  reaction  is  rapid  and 
standardized  solutions  of  bromine  in  acetic  acid  or  carbon  tetrachloride 
can  often  be  used  to  titrate  such  hydrocarbons  and  determine  the  de- 
gree of  unsaturation.29  However,  substitution  of  hydrogen  sometimes 
takes  place  and  the  well-known  analytical  methods  of  Hiibl,  Hanus 
and  Wijs,  which  are  of  such  value  with  unsaturated  fatty  oils,  cannot 
be  relied  upon  to  give  correct  results  in  the  case  of  the  terpenes  and 
the  higher  ethylene  homologues  derived  from  petroleum.30  Bromine 
addition  products  are  sometimes  crystalline  solids  and  thus  serve  for 
purposes  of  identification,  as  in  the  case  of  butadiene,  the  tetrabro- 
mide31  melting  at  118°,  and  limonene  and  dipentene  whose  tetrabro- 
mides  melt  at  104°-105°  and  124°  respectively.  The  addition  of  halo- 
gen acids  has  already  been  referred  to  in  the  section  dealing  with  the 
preparation  of  halogen  derivatives.  The  addition  of  bromine  is  made 
use  of  in  the  analytical  chemistry  of  rubber  and  a  chlorinated  rub- 
ber 32  has  recently  appeared  on  the  market. 

Hypochlorous  acid  reacts  with  ethylene  bonds  more  readily  than 
concentrated  sulfuric  acid,  forming  chlorohydrins.  Thus  ethylene  re- 
acts readily  with  cold  dilute  solutions  of  hypochlorous  acid,  and  also 
other  substances,  which  are  inert  or  react  only  very  slowly  with 
sulfuric  acid  at  ordinary  temperatures,  yield  chlorohydrins,  for  ex- 
ample, cinnamic  acid,  allyl  bromide,  maleic  acid  and  the  higher  ethyl- 
ene homologues.  Solutions  of  chlorine  water  give  nearly  theoretical 

**Ber.  52,  B.  51   (1919). 

»Cf.  v.  Soden  and  Zeitschel,  Ber.  S6,  266  (1903). 

10  For  description  and  details  for  carrying  out  these  determinations  see  Leach, 
"Food  Analysis,"  pp.  488-530,  4th  Ed.  Lewkowitsch,  "Oils,  Fats  and  Waxes,"  Vol.  I, 
p.  393.  See  Faragher  and  Garner,  J.  Ind.  &  Eng.  Chem.  13f  1044  (1921). 

31  A    low  melting  modification   melting  at  37.5°   is  also  known. 

"  The  product  carries  the  trade  name  "Duroprene"  and  appears  to  have  value  as 
a  varnish  film  resistant  to  corrosive  vapors  or  acids. 


124      CHEMISTRY  OF  THE  NON-BENZEN01D  HYDROCARBONS 

yields  of  ethylene  chlorohydrin  but  other  unsaturated  hydrocarbons 
that  react  energetically  with  chlorine  also  yield  dichlorides.  In  such 
cases  better  yields  of  chlorohydrins  are  obtained  by  employing  dilute 
solutions  of  alkali  hypochlorite  which  yield  free  hypochlorous  acid  by 
hydrolysis  and  contain  no  free  chlorine.  Thus  Walker 33  employs  so- 
dium hypochlorite  in  the  presence  of  sodium  bicarbonate  to  prepare 
amylene  chlorohydrins  (carbonic  acid  is  a  stronger  acid  from  the  ioni- 
zation  standpoint  than  hypochlorous  acid) .  The  chlorohydrins  of  ethyl- 
ene, propylene,  butylene,34  amylenes,35  and  hexylenes  are  best  known. 
Propylene  and  hypochlorous  acid  yields  a  mixture  of  the  two  isomers 
CH3CHOH.CH2C1  and  CH3CHC1.CH2OH.  By  the  action  of  hydro- 
gen chloride  on  propylene  oxide  both  isomeric  chlorohydrins  are  ob- 
tained as  has  been  shown  by  an  examination  of  their  rate  of  hydroly- 
sis.36 Isobutylene  and  the  amylenes  also  yield  a  mixture  of  isomeric 
chlorohydrins.37  All  of  these  simpler  chlorohydrins  yield  alkylene 
oxides  when  treated  with  concentrated  caustic  alkali,  and  slow  hydroly- 
sis in  the  presence  of  sodium  bicarbonate  gives  good  yields  of  the  gly- 
cols.  The  utilization  of  the  ethylene  and  propylene  in  oil  gas  and 
petroleum  still  gases  in  this  manner  has  recently  been  attempted  on 
an  industrial  scale. 

On  heating  the  simpler  chlorohydrins  with  water,  aldehydes,  or  ke- 
tones  are  formed.  Thus  2-chloro-3-hydroxybutane  is  completely  con- 
verted to  methyl  ethyl  ketone  in  3  hours  at  120°.  Propylene  chloro- 
hydrins give  acetone  and  propionic  aldehyde  and  the  chlorohydrin  of 
trimethyl  ethylene  similarly  yields  methyl  isopropyl  ketone.38 

The  reaction  of  hypochlorous  acid  with  other  unsaturated  sub- 
stances, for  example,  the  terpenes,  unsaturated  petroleum  oils  and 
fatty  oils  has  been  very  little  studied.  Pinene  yields  a  mixture  of 
products,39  among  which  is  pinol  oxide,  C10H1602,  which  oxide,  unlike 
cineol,  is  very  easily  hydrolyzed  by  dilute  acids  to  a  glycol.  The  di- 
chlorohydrine  C10H1802C12  is  also  formed,  the  bridged  ring  being 
opened.  The  substance  cis-pinolglycol-2-chlorohydrin,  C10H1702C1,  is 
very  stable  to  aqueous  alkalies  as  is  also  the  chlorohydrin  obtained 
from  camphene,40  C10H16HOC1.  Large  proportions  of  chlorination 

88  U.  S.  Pat.  972,952  ;  972,954. 

84  Henry,  Bull.  Acad.  roy.  Belg.  1906.  523  ;  Compt.  r&nd.  142.  493  ;  Krassuski,  Chem. 
Zentr.  1901,  I,  995. 

"Carius,  Ann.  126,  199   (1863)  ;  Umnowa,  Chem.  Zentr.  1911,  I,  1278. 
"Smith,  Z.  physik,  Chem,  93,  59    (1918)  ;  Cf.  Michael,  Ber.  39,  2785    (1906). 

87  Henry,  loc.  cit. 

"Krassuski,  Chem.  Zentr.  1902,  II,  20. 

88  Wagner  &  Slawinski,  Ber.  S2,  2064  ;  Henderson  &  Marsh.  J.  Chem.  Soc.  119,  1492 
(1921). 

40  Slawinski,  Chem.  Zentr.  1906,  I,  137. 


THE  ETHYLENE  BOND  125 

products  are  also  formed  in  the  case  of  camphene  and  this  together 
with  the  fact  that  these  chlorohydrins  are  relatively  stable  and  are 
not  easily  converted  to  glycols  perhaps  accounts  for  the  fact  that 
hypochlorous  acid  has  not  become  an  instrument  of  research  in  this 
series. 

The  influence  of  constitution  and  the  presence  of  substituent  atoms 
or  groups  on  the  addition  of  water  and  behavior  toward  acids,  or 
their  aqueous  solutions,  is  very  pronounced.  A  few  substances  possess- 
ing double  bonds,  carbon  to  carbon,  react  with  water  energetically, 
for  example,  ketene  H2C  =  CO  and  carton  suboxide,  OC  =  C  =  CO, 
whose  behavior  toward  water  resembles  that  of  acid  anhydrides.  The 
unsaturated  hydrocarbons  themselves,  however,  do  not  react  with  wa- 
ter directly  although  Engelder  observed  indications  that  the  dehydra- 
tion of  alcohol  to  ethylene  and  water  in  the  presence  of  alumina  or 
kaolin,  is  reversible.41 

Aqueous  solutions  of  organic  acids,  particularly  formic  and  oxalic 
acids,  effect  hydration  in  certain  instances,  for  example 

(CH3)  2C  =  CH  .  CH3  +  H20  *±  (CH8)  2  .  C  .  OH  .  CH2CH3 

but  the  method  is  by  no  means  general  and  is  of  no  preparative  value. 
The  formation  of  esters  of  organic  acids  and  defines  on  heating  or  in 
the  presence  of  other  substances,  such  as  zinc  chloride  or  sulfuric  acid, 
often  gives  excellent  yields.  Heptylene  and  acetic  acid  heated  in  an 
autoclave  or  sealed  tube  to  300°  yields  heptyl  acetate.42  Amylene  and 
acetic  acid  react  at  ordinary  temperatures  in  the  presence  of  zinc  chlo- 
ride, but  the  yield  is  greatly  diminished  by  the  formation  of  polymers. 

(CH8)2C  =  CH.CH3  +  CH3C02H 

(CH3)2C(02C.CH3).CH2CH3 


polymers 

In  most  cases,  better  results  are  obtained  by  the  method  of  Ber- 
tram and  Walbaum,  in  which  process  the  olefine  is  dissolved  in  an 
excess  of  acetic  acid  and  a  relatively  very  small  quantity  of  sulfuric 
acid  is  added.43  The  presence  of  water  greatly  retards  the  acetylation. 
This  reaction  does  not  appear  to  have  been  applied  industrially  to  the 
acetylation  of  amylenes  or  other  olefines  derived  from  petroleum,  but 

41  J.  Phys.  Chem.  21,  676    (1917). 

«Behal  and  Desgrez,  Oompt.  rend.  114,  676   (1892), 

«J.  prakt.  Chem.  W,  7   (1894). 


126      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

has  been  conspicuously  successful  in  the  acetylation  of  camphene  to 
bornyl  acetate  (see  Artificial  Camphor) .  Barbier  and  Grignard  **  rec- 
ommend benzene  sulphonic  acid  instead  of  sulfuric  acid  to  promote  the 
reaction  and  state  that  the  addition  of  acetic  anhydride  to  the  reaction 
mixture  increases  the  yield  of  ester.  Pinene  yields  mainly  a-terpineol 
acetate. 

Anhydrous  oxalic  acid  and  pinene  at  120°  yield  bornyl  oxalate  and 
formate,  which  process  formed  the  basis  of  the  first  artificial  camphor 
process  to  be  attempted  on  an  industrial  scale.45  A  large  number  of 
patents  have  been  issued  covering  the  use  of  other  organic  acids  in 
making  borneol  esters.  Just  as  hydrogen  chloride  containing  a  little 
moisture  yields  chiefly  dipentene  dihydrochloride,  concentrated  formic 
acid  (98-99%)  yields  mainly  terpinyl  formate,  the  bridged  ring  being 
opened  in  each  case. 

The  results  of  treating  unsaturated  hydrocarbons  with  sulfuric 
acid  is  of  considerable  interest  in  connection  with  the  hydration  of 
olefmes,  including  the  terpenes,  and  also  the  refining  of  petroleum  dis- 
tillates. The  results  include  changes  of  the  following  nature:  re- 
arrangement, or  shift  in  the  position  of  the  double  bond,  polymeriza- 
tion, formation  of  mono  and  dialkyl  sulfuric  esters,  and  hydration  to 
alcohols. 

The  tendency  of  the  defines  and  substituted  ethylenes  to  react 
with  sulfuric  acid  is  distinctly  less  than  their  tendency  to  react  with 
bromine.  Thus  cinnamic  and  fumaric  acids  readily  yield  dibromides 
but  are  not  affected  by  ordinary  concentrated  sulfuric  acid  at  25°. 
The  substitution  for  the  hydrogen  of  ethylene,  of  groups  which  impart 
a  strongly  electronegative  character,  results  in  decreased  reactivity  to 
sulfuric  acid.  Thus  cinnamic  and  fumaric  acids  are  inert,  and  dichlo- 
roethylene  and  trichloroethylene  are  only  very  slowly  acted  upon  by 
sulfuric  acid  at  ordinary  temperatures.  Allyl  bromide  is  also  more 
stable  to  sulfuric  acid  than  is  propylene.  The  substitution  of  groups 
which  impart  an  electropositive  character,  such  as  methyl  groups,  re- 
sults in  greatly  increased  reactivity  to  sulfuric  acid.  Isobutene, 
(CH3)2C  =  CH2  is  rapidly  and  completely  dissolved  by  sulfuric  acid, 
63%  H2S04,  at  17°.  Also  tetramethylethylene  (CH3)2C  =  C(CH3)2 
reacts  readily  and  completely  with  77%  acid  at  ordinary  tempera- 
tures. Of  the  two  amylenes 

"Compt.  rend.  US,  1425   (1907)  ;  Bull.  Soc.  Chim.   (4),  5,  512   (1909). 
U 


THE  ETHYLENE  BOND  127 

CH3  C2H5 

>  CHCH  =  CH0      and  >  C  =  CH0 

CH3  CH3 

the  latter  dissolves  .more  readily  in  66%  acid.46  Results  very  closely 
parallel  to  these  have  been  noted  in  the  case  of  the  reactions  of  amyl- 
enes  and  halogen  acids.47  Michael  and  Brunei  believed  that  in  the  ali- 
phatic hydrocarbon  series  the  tendency  to  form  alcohols  and  alkyl  sul- 
furic  esters  decreases  with  increasing  molecular  weight,  this  result  ap- 
pearing to  be  maximum  with  the  amylenes  and  hexylenes.  With  in- 
creasing molecular  weight  polymerization  becomes  the  principal  result, 
which  result,  however,  may  possibly  be  preceded  by  alcohol  forma-' 
tion.48  The  difference  in  the  final  results  may,  therefore,  be  due  in  large 
part  to  the  relatively  greater  stability  of  the  simpler  alcohols.  Thus  un- 


C2H5 

der  the  same  conditions  3-ethylpentene  (2)          >C  =  C<          yields 

C2H5  H 

72%  alcohol  and  12%  polymers  and  2-methylundecene(2)  yields 
97%  polymers  ancj  only  a  trace  of  alcohol.  Secondary  octyl  alcohol, 
octane-ol(2),  treated  with  95%  sulfuric  acid  at  20°  gives  a  yield  of 
octene  polymers  C16H32  and  C24H48,  increasing  with  the  time  of  stand- 
ing. A  mixture  of  octene  (1)  and  octene  (2)  treated  with  sulfuric 
acid,  with  cooling,  yields  chiefly  a  mixture  of  the  di-  and  tri-polymers.49 

In  a  study  of  a  series  of  pure  unsaturated  hydrocarbons  Brooks 
and  Humphrey  noted  that  the  polymers  were  always  more  stable  to 
sulfuric  acid  than  the  parent  olefines.50  Kondakow  noted  a  closely 
parallel  behavior  in  the  reaction  of  hydrogen  chloride  and  isobutene 
and  its  polymers.51  These  results  can  be  sxpressed  in  another  way, 
e.  g.,  unsaturated  hydrocarbons  are  more  highly  polymerized,  to  higher 
boiling,  more  viscous  polymers,  by  100%  sulfuric  acid  than  by  95% 
acid  and  the  latter  will  produce  a  higher  degree  of  polymerization  than 
85%  acid. 

The  mechanism  of  these  changes  is  very  obscure.  It  has  generally 
been  assumed  that  the  alcohols,  formed  by  treating  unsaturated  hydro- 
carbons with  sulfuric  acid  or  dilute  sulfuric  acid,  were  a  result  of  the 
hydrolysis  of  the  alkyl  sulfuric  esters  first  formed, 

49  Michael  and  Brunei,  Am.  Chem.  J,  41,  118    (1909).* 

"Eltekow,  Ber.  10,  707   (1877)  ;  Konowalow,  Per.  IS,  2395    (1880). 

48  Cf.  Brooks  and  Humphrey.  J.  Am.  Chem.  Soc.  10,  822   (1918). 

49  Rossolimo,  Ber.  27,  626   (1894). 

60  J.  Am.  Chem.  Soc.  1,0,  822   (1918). 

61  J.  prakt.  Chem.   (2)   54,  449   (1896). 


128      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

RCH  RCH.  RCH2 

|  +H20 >     | 

RCHOSO.H  RCHOH 


JLVV~/XJL*  J.VV-/J.J-2 

||     +H2S04 »     I  +H20 >     |  +H2S04 

RCH  EOF 


Thus  ethyl-hydrogen  sulfate  can  be  hydrolyzed  to  give  ethyl  alco- 
hol but  the  relative  stability  of  this  ester  is  indicated  by  the  fact  that  a 
dilute  solution  of  ethyl-sodium  sulfate  is  hydrolyzed  in  8  days  at  60° 
only  to  the  extent  of  16  per  cent.52  The  mono  or  acid  sulfuric  esters 
of  amylenes,  hexenes  and  heptenes  are  not  appreciably  hydrolyzed 
on  diluting  with  water  at  ordinary  temperatures  and  their  hydrolysis 
in  dilute  solution  at  100°  is  very  slow.  However,  when  these  olefines 
are  dissolved  in  cold  sulfuric  acid  and  the  clear  homogenous  acid  solu- 
tion diluted  with  water  at  0°  the  free  alcohols  are  precipitated  imme- 
diately in  yields  sometimes  as  high  as  70  per  cent  of  the  theory.  Fur- 
ther dilution  or  complete  extraction  of  the  alcohols  remaining  dissolved 
by  means  of  an  immiscible  solvent  causes  no  hydrolysis  of  the  alkyl 
sulfuric  esters  which  remain  in  the  aqueous  solution.  The  barium 
salts  of  these  acid  esters  can  be  easily  isolated  by  slow  evaporation 
without  appreciable  decomposition.  Although  these  alkyl  sulfuric 
esters  can  be  saponified  by  caustic  alkali  or  hydrolyzed  by  prolonged 
boiling  or  steaming,  they  are  not  hydrolyzed  to  alcohols  under  the 
conditions  which  obtain  in  the  separation  of  the  alcohols  from  these 
sulfuric  acid  mixtures.  Also  the  highest  yields  of  alcohol  are  obtained 
when  employing  sulfuric  acid  containing  water,  greater  yields  of  alcohol 
being  obtained  with  85  per  cent  acid  than  with  95  per  cent  or  100  per 
cent  acid,  or  with  benzene  sulfuric  acid. 

To  account  for  these  facts  the  theory  has  been  proposed 53  that  the 
addition  of  water  to  olefines  with  formation  of  free  alcohols,  in  cold 
solutions,  is  due  to  reaction  with  the  monohydrate  of  sulfuric  acid 
H2S04.H20,  or  higher  hydrates.  The  monohydrate,  or  orthosulfuric 
acid,  is  usually  regarded  as  having  the  constitution 

HO  OH 

Vo 

/   \ 
HO  OH 

B2Linhart,  Am.  J.  Sci.  35,  283  (1913)  ;  Evans  and  Albertson  mention  that  in  the 
system  C2HBOH+H2SO4±5C2HBH.SO4  +  H2O  the  dilution  of  the  mixture  by  titration  does 
not  cause  appreciable  hydrolysis.  [J.  Am.  Chcm.  Soc.  39,  456  (1917).] 

63  Brooks  and  Humphrey,  loc.   cit. 


THE  ETHYLENE  BOND 


129 


It  is  practically  certain  that  esters  of  this  acid  would  have  quite  differ- 
ent degrees  of  stability  and  quite  different  rates  of  hydrolysis  than  the 
known  relatively  stable  esters  of  ordinary  sulfuric  acid. 

The  hydration  of  pinene  to  terpin  hydrate  C10H18(OH)2.H20  by 
dilute  aqueous  acids  has  long  been  known.  Heating  terpin  hydrate 
with  dilute  sulfuric  or  phosphoric  acids  results  in  partial  decomposition 
to  terpineol,  which  process  is  carried  out  industrially.  Wallach54 
has  pointed  out  the  marked  effect  of  differences  of  constitution  on  the 
rate  of  hydration  of  five  menthenols. 


CH3 


GIL 


c-OH 


CH3        CH2 


/\ 


The  menthenols  I  and  II  react  readily  with  5%  sulfuric  acid 
at  ordinary  temperature  and  III  a  little  less  rapidly.  Menthenols  IV 
and  V  react  so  much  slower  than  I,  II  and  III,  that  separation  of 
these  two  groups  can  be  effected  in  this  way,  taking  advantage  of  the 
fact  that  the  resulting  terpins  are  not  volatile  with  steam.  Other 
substances  having  a  methene  group  in  a  side  chain  are  also  very  easily 
hydrated  by  dilute  sulfuric  acid,  for  example,  dihydrocarveol  and  iso- 
pulegol, 


OH 


/\ 

dihydrocarveol 

"Ann.  S60,  82   (1908). 


130      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


H 


\ 

isopulegol 

The  facility  with  which  such  unsaturated  groups  are  hydrated  af- 
fords an  explanation  of  the  rearrangement  of  many  unsaturated  sub- 
stances in  the  presence  of  dilute  mineral  acids,  for  example, 


=  0 


terpinenes 


THE  ETHYLENE  BOND  131 

The  rearrangement  of  2-methylbutene-(3)  to  trimethylethylene  by 
dilute  acids  is  probably  effected  in  the  same  manner,55 

CH3  CH3  OH       CH3 

>CHCH  =  CH2->         >CHCH<         -* 
CH3  CH3  CH3      CH3 

Thus  when  commercial  amylene  is  hydrated  by  sulfuric  acid,  the 
resulting  alcohol  is  chiefly  "amylene  hydrate"-  or  dimethylethylcar- 
binol,56  obtained  in  very  pure  condition  from  trimethylethylene,57- 

CH3  CH3 

>C=CH.CH3 >         >C.OH.CH2CH3 

CH3  CH3 

Amylene  and  alcoholic  sulfuric  acid  yields  amyl  methyl  ether.58 

Unsaturated  Hydrocarbons  and  the  Refining  of  Petroleum  Oils. 

From  the  foregoing  section,  it  is  clear  that  treatment  of  petroleum 
distillates  with  sulfuric  acid  does  not  completely  remove  the  unsatu- 
rated  hydrocarbons  but  partly  polymerizes  them.  The  polymers  thus 
formed  are  not  removed  with  the  "acid  sludge,"  but  are  found  in  the 
treated  and  washed  oil.  This  accounts  for  the  relatively  large  pro- 
portions of  high  boiling  fractions  usually  obtained  when  a  so-called 
cracked  gasoline  is  refined  by  sulfuric  acid  and  then  redistilled.59 
When  the  sulfuric  acid  from  a  refining  operation  is  diluted  with  water 
an  "acid  oil"  is  precipitated  which,  in  the  case  of  gasoline  and  kerosene, 
has  a  pronounced  odor  due  chiefly  to  the  alcohols  present.  Acid  oil 
from  the  lower  boiling  distillates,  gasoline  and  kerosene,  contain  little 
tarry  matter.  Pure  mono  olefines  of  the  aliphatic  series  do  not  yield 

55  On  account  of  this  tendency  of  unsaturated  substances  to  rearrange,  in  the 
presence  of  sulfuric  or  other  mineral  acids,  the  method  of  determining  the  constitution 
of  unsaturated  hydrocarbons  by  oxidation  by  chromic  acid  is  not  to  be  relied  upon. 
The  same  consideration  applies  to  the  oxidation  of  certain  alcohols,  for  example,  a 

CHa 
substance  containing  the  group  >  CH.CH2CHOH  —  CHa — R  would  undoubtedly 

CH3 
yield  a  mixture  of  oxidation  products,  among  which  acetone  derived  from 

>  C  =  CH  —  R    would  be  found. 
CH3  x 

86  It  will  be  noted  that  the  alcohols  derived  from  the  hydration  of  ethylene  double 
bonds  are  always  tertiary  or  secondary  alcohols ;  the  hydroxyl  group  becomes  attached 
to  the  more  "positive"  carbon  atom.  The  industrial  manufacture  of  alcoholic  solvents 
from  low-boiling  olefines,  derived  from  petroleum  or  the  commercial  "amylene"  obtained 
as  a  by-product  of  the  manufacture  of  oil  gas  or  Pintsch  gas,  has  been  attempted. 
The  "acid  oils"  obtained  by  diluting  the  sulfuric  acid  used  in  refining  gasoline  made 
by  pressure  distillation  or  similar  methods  also  contains  secondary  and  tertiary 
alcohols.  Although  the  tertiary  alcohol,  dimethyl  ethyl  carbinol,  boiling  point  102°, 
is  an  excellent  solvent  for  cellulose  nitrate,  it  cannof  be  acetylated  by  ordinary 
methods.  Like  the  majority  of  tertiary  alcohols,  it  has  a  camphor-like  odor. 

67  Wischnegradsky,  Ber.  10,  81   (1877)  ;  Ann.  190,  332,  366   (1878). 

58  Reychler,  Chem.  Zentr.  1907,  I,   1125 ;   Henry,  Bull.  Acad.  roy.  Belg.  1906,  261. 

59  Cf.  Brooks  &  Humphrey,  loc.  cit.     The  proportions  of  such  high  boiling  polymers 
contained  in  a  refined  oil  will  be  greater  if  the  duration  of  the  treating  operation  is 
prolonged,  or  the  mixture  allowed  to  stand. 


132      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

tars  with  concentrated  sulfuric  acid  at  ordinary  temperatures,  but 
diolefines,  particularly  those  containing  conjugated  double  bonds,  re- 
act very  energetically  with  sulfuric  acid,  forming  tars  and  reducing  the 
acid.  Thus  highly  unsaturated  oils,  made  at  very  high  temperatures, 
such  as  crude  benzene  derived  from  oil  gas  or  Pintsch  gas  manufac- 
ture, react  violently  with  sulfuric  acid  on  account  of  the  cyclohexadiene 
and  other  di-olefines  contained  in  such  oils. 

When  gasoline  or  kerosene  containing  unsaturated  substances  is  re- 
fined by  sulfuric  acid  and  then  redistilled,  liberation  of  sulfur  dioxide 
is  always  noted.  This  is  present  in  the  alkali  washed  oil,  prior  to  dis- 
tillation, in  the  form  of  neutral  or  dialkyl  esters  of  sulfuric  acid, 
(RO)2S02.  These  esters  are  decomposed  on  heating,  yielding  tarry 
matter  and  sulfur  dioxide.  Theory  indicates  that  refining  with  a  mini- 
mum of  sulfuric  acid  leads  to  the  formation  of  neutral  or  dialkyl 
esters,  which  partly  remain  dissolved  in  the  treated  oil,  and  greater 
proportions  of  sulfuric  acid  favor  the  formation  of  acid  or  mono-alkyl 
esters  which  are  readily  washed  out.  Practice  confirms  this  suppo- 
sition; oils  refined  by  relatively  small  quantities  of  acid  contain  more 
sulfur,  in  a  form  appearing  as  S02  on  heating,  than  oils  treated  with 
relatively  larger  quantities  of  acid. 

It  is  also  evident  from  the  foregoing  section  that  the  per  cent  by 
volume  of  unsaturated  hydrocarbons  contained  in  a  certain  distillate 
cannot  be  accurately  ascertained  by  treating  with  sulfuric  acid.  The 
usual  practice  has  been  to  determine  the  loss  on  treating  with  concen- 
trated sulfuric  acid  but  it  is  evident  that  the  formation  of  polymers 
entirely  destroys  the  quantitative  character  of  such  a  determination. 
Such  tests  are  of  qualitative  value  only.  The  results  obtained  by  em- 
ploying sulfuric  acid,  Sp.  Gr.  1.84  are  too  low,  at  least  for  gasolines 
and  kerosene,  and  the  results  obtained  when  fuming  sulfuric  acid  is 
employed  are  too  high  since  Worstall 60  has  shown,  and  it  is  a  matter 
of  common  experience  that  fuming  sulfuric  acid  attacks  saturated  hy- 
drocarbons. Fuming  sulfuric  acid  also  sulfonates  any  aromatic  hydro- 
carbons which  may  be  present.  No  accurate  quantitative  method  is 
now  known  for  the  determination  of  the  percent  by  volume  of  un- 
saturated hydrocarbons  in  a  mixture  containing  also  saturated  hydro- 
carbons (probably  of  various  types)  and  aromatic  or  benzenoid  hy- 
drocarbons. 

60  Am.  Chem.  J.  20,  664  (1898).  The  original  method  as  recommended  by  Kramer 
and  Bottcher  specified  the  use  of  fuming  sulfuric  acid.  Worstall  obtained  yields  of 
30  to  40%  of  the  sulfonic  acids  of  n.hexane,  n. heptane  and  n.octane.  According  to 
Markownikow  naphthenes  are  simultaneously  sulfonated  and  oxidized  by  fuming 
sulfuric  acid.  (J.  Rusa.  Phys.-Chem.  Soc.  1892,  141.) 


THE  ETHYLENE  BOND  133 

Other  Reactions  of  Olefines. 

The  oxidation  of  unsaturated  hydrocarbons  by  air  or  oxygen  is 
nearly  as  general  a  reaction  as  the  reaction  with  ozone,  although  much 
less  energetic  than  the  latter.  The  oxidation  of  turpentine,  and  the 
formation  of  what  are  now  recognized  as  peroxides,  was  noted  by 
Schoenbein  in  his  well-known  studies  of  oxidation,  hydrogen  peroxide 
and  ozone  and,  Berthelot  like  Schoenbein,  wrote  of  ozone  formation 
when  turpentine  is  oxidized  by  air.  Fudakowski 61  noted  that  light 
petroleum  fractions  acquired  oxidizing  properties  similar  to  oxidized 
turpentine,  when  these  oils  were  exposed  to  light  and  air.  Kingzett 62 
first  proved  that  ozone  was  not  present  and  attributed  the  ability  of 
such  oxidized  material  to  effect  the  oxidation  of  other  substances,  to 
the  presence  of  a  peroxide  or  "hydrated  oxide."  A  great  deal  of  ex- 
perimental work  on  this  subject  was  done  many  years  ago,  but  the 
whole  matter  was  greatly  clarified  by  Engler  and  Weissberg,63  Bach 64 
and  others  and  the  general  character  of  the  "autoxidation"  of  these 
unsaturated  hydrocarbons  finds  close  parallels  in  the  air  oxidation 
and  resinification  of  rubber,  particularly  prior  to  vulcanization,  the  oxi- 
dation and  consequent  deterioration  of  rosin,  copals  and  varnishes,  the 
drying  of  linseed  and  similar  oils  and  the  deterioration  of  many  sub- 
stances by  oxidation  brought  about  by  some  second  unsaturated  sub- 
stance occurring  with  it,  for  example,  the  destruction  of  cellulose  fiber 
when  in  contact  with  lignin  or  rosin  sizing.  Engler  and  Weissberg 
showed  that  "the  oxygen  combines  as  molecular  oxygen,"  and  that  "a 
peroxide  is  formed  which  may  then  rearrange  to  ordinary  oxides,  or 
may  react  upon  other  unoxidized  substance."  In  the  case  of  turpen- 
tine, the  per  cent  of  peroxides  present  after  oxidation  at  temperatures 
up  to  160°  decreases  rapidly  with  rising  temperature,  and  a  sample 
rich  in  peroxides,  formed  at  low  temperature,  is  rapidly  altered  by 
heating,  the  peroxides  being  decomposed,  with  further  oxidation  of  the 
turpentine.  As  surmised  by  Kingzett  and  later  shown  conclusively  by 
Clover  and  Richmond65  organic  peroxides  are  hydrolyzed  by  water 
forming  hydrogen  peroxide,  which  accounts  for  the  many  positive  re- 
actions for  this  substance  obtained  by  the  earlier  investigators.  Engler 

"Ber.  6,  106  (1873). 

62  J.   Chem,  8oc.  12,  511    (1874). 

^Vorgange  d.  Autoxydation,  1904;  Ber.  SI,  3050    (1898). 

"Compt.  rend.  124,  2951   (1897). 

*>Am.  Chem.  J.  29,  179  (1903).  The  oxidizing  power  of  old  oxidized  turpentine 
has  been  utilized  in  medicine,  as  an  antiseptic,  as  an  antidote  for  certain  poisons, 
acn  as  yellow  phosphorus,  and  the  more  stable  peroxides,  such  as  benzoyl  peroxide 
and  benzoylacetyl  peroxide  studied  by  Clover  and  Richmond  have  been  tried  as  anti- 
septics for  diseases  of  the  intestinal  tract. 


134      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

and  Weissberg  were  able  to  isolate  the  peroxides  of  amylene,  trimethyl 
ethylene,  and  hexylene  in  fair  degree  of  purity. 

Rupture  of  the  ethylene  bond  by  autoxidation  has  been  noted  in 
many  instances,  aldehydes,  ketones  or  acids  being  formed ;  the  methene 
group  >C  =  CH2  splits  with  the  formation  of  formaldehyde  or  formic 
acid,  as  in  the  case  of  |3-pinene,  limonene66  and  (3-phellandrene.67 
Willstatter  sought  a  catalyst,  in  the  hope  that  oxidation  of  unsaturated 
substances  might  be  effected  as  easily  as  hydrogenation  in  the  presence 
of  fine  nickel  but,  although  metallic  osmium  appears  to  catalyse  the 
reaction  and  cyclohexene  was  thus  oxidized,  in  acetone  solution,  to 
cyclohexenol,  the  method  has  had  no  further  extension.68  However,  the 
industrial  use  of  catalysts  in  promoting  air  oxidation  has  long  been 
known  in  the  paint  and  varnish  industry  where  salts  or  resinates  of 
manganese,  lead  and  cobalt  are  widely  used.  The  effect  of  light  in 
accelerating  such  oxidations  has  also  long  been  known.  In  the  autoxi- 
dation of  styrene  marked  polymerization  occurs,  but  in  direct  sunlight 
fission  of  the  side  chain  occurs  with  the  formation  of  benzaldehyde 
and  formaldehyde.69  The  effect  of  sunlight  in  promoting  autoxidation 
has  been  studied  by  Ciamician  and  Silber 70  whose  investigations  also 
show  that  oxidation  under  these  conditions  is  by  no  means  limited  to 
substances  containing  an  ethylene  bond,  but  very  stable  ketones  such 
as  cyclohexanone  and  menthone  are  oxidized  and  their  carbocyclic 
structure  ruptured.  Vanadium  pentoxide71  has  come  into  vogue  as 
catalyst  for  oxidizing  a  wide  variety  of  substances  by  means  of  air  at 
elevated  temperatures,  for  example,  naphthalene  to  phthalic  acid  or  an- 
hydride. These  conditions  are  quite  different  from  those  commonly  un- 
derstood as  autoxidation.  The  oxidation  of  olefines  or  saturated  non- 
benzenoid  hydrocarbons  by  this  method  has  not  been  reported,  but 
judging  from  their  oxidation  under  very  similar  conditions  the  resulting 
products  would  probably  be  water,  carbon  dioxide,  unchanged  hydro- 
carbon and  small  yields  of  the  simpler  aldehydes  and  acids. 

Closely  related  to  the  subject  of  autoxidation  is  the  method  dis- 
covered by  Prileshajew72  who  has  shown  that  benzoyl  peroxide, 
C6H5CO.O.OH,  combines  directly,  in  cold  neutral  solvents,  with  sub- 

"Blumann  &  Zeitschel,  Ber.  47,  2623  (1914).  For  the  oxidation  of  ethylene  to 
formaldehyde  see  Ethylene,  Willstatter,  Ann.  422  (1921). 

87  Wallach,  Ann.  348,  30  (1905)  ;  362,  291  (1908)  ;  Kingzett  has  noted  the  corrosion 
of  metal  containers,  used  for  turpentine,  due  to  solution  of  the  metal  by  formic  acid. 

«*Ber.  46,  2952    (1913). 

08  Stobbe,  J.  prakt.  Chem.  1914,  551. 

™Ber.  42,  1510   (1909)  ;  46,  3077    (1913). 

71  Senderens  employed  it  for  oxidizing  alcohols.  [J.  Chem.  Soc.  1913,  I,  814.] 
Naphthalene  and  benzene  are  also  oxidizable  by  its  aid. 

"Ber.  42,  4812   (1909)  ;  J.  Russ.  Phys.-Chem  Soc.  43,  609   (1911)  ;    44,  613    (1912). 


THE  ETHYLENE  BOND  135 

stances  containing  an  ethylene  bond.  The  initial  product  readily  de- 
composes to  give  an  oxide  of  the  original  olefine,  and  these  oxides  are 
generally  very  easily  hydrolysed  to  glycols.  The  method  was  applied 
particularly  to  the  oxidation  of  linalool,  geraniol,  citral  and  citronellal. 
The  hydrocarbons  di-isobutylene,  decylene  and  the  terpenes  limonene 
and  pinene  yield  oxides,  which  may  be  hydrolysed  to  glycols,  which 
suggests  that  the  autoxidation  of  other  unsaturated  hydrocarbons,  for 
example,  unsaturated  petroleum  hydrocarbons,  may  lead  to  the  for- 
mation of  glycols  as  one  of  the  minor  products,  when  moisture,  suffi- 
cient for  hydrolysis,  is  present. 

Probably  the  best  known  method  of  oxidizing  the  olefine  group 
for  the  purpose  of  determining  the  constitution  of  organic  substances 
is  that  of  oxidizing  by  cold  dilute  potassium  permanganate.  Thus 
trimethyl  ethylene  gives  a  very  good  yield  of  the  corresponding  gly- 
col,73  and  diallyl  yields  a  hexyl  erythrite.  An  excess  of  permanganate 
results  in  further  oxidation  of  the  glycol  with  a  break  in  the  carbon 
atom  chain,  as  in  the  rupture  of  the  double  bond  in  ct-pinene  to  form 
pinonic  acid.74  This  break  in  the  carbon  atom  structure  of  a  substance 
does  not  always  occur  at  the  point  at  which  the  double  bond  was  origi- 
nally located,  as  has  been  shown  in  the  case  of  carvenone  and  ter- 
pinenol-(4).  Nevertheless,  this  method  of  oxidation  and  the  ozone 
method  are  the  most  reliable  means  yet  discovered  of  determining  the 
position  of  ethylene  bonds  in  organic  substances. 

The  reaction  of  sulfur  with  unsaturated  hydrocarbons  has  been 
little  investigated.  According  to  H.  Erdmann75  sulfur  exists  at  160° 
largely  as  S3  or  thiozone,  and  at  this  temperature  he  succeeded  in 
forming  a  "thiozonide"  of  linalyl  acetate  C12H2002S3  and  was  unable 
to  obtain  a  derivative  containing  less  than  three  atoms  of  sulfur. 
Friedmann,76  however,  isolated  a  compound  C10H12S  by  reacting  upon 
dicyclopentadiene  with  sulfur.77  By  heating  sulfur  and  turpentine 
together  at  150°  a  viscous  product  containing  30  to  50  per  cent  of  sul- 
fur can  be  obtained.78 

The  reaction  of  sulfur  with  unsaturated  hydrocarbons  is  of  interest 
in  connection  with  the  vulcanization  of  rubber.  In  addition  to  the  evi- 
dence furnished  by  the  ozone  reaction,  the  action  of  oxygen  upon  thin 

'Wagner,  Ber.  U,  1230,  3343   (1888). 
*Baeyer,  Ber.  29,  22    (1896). 
3  Ann.  362,  133    (1908). 
*  Ber.  1,9,  50,  683   (1916). 

7  Koch,  German  Pat.  236,  490   (1909),  prepares  sulfur  derivatives  of  terpenes  by 
heating  with  sulfur  until  hydrogen  sulflde  is  evolved. 
"Pratt,  U.  S.  Pat.  1,349,909. 


136      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

films  of  rubber  indicates  the  presence  of  two  double  bonds  for  each 
C10H16  complex,  two  molecules  of  oxygen  being  combined,79  and  when 
treated  with  sulfur  chloride 80  the  limit  of  the  reaction  corresponds 
more  closely  to  Weber's  (C10H16S2Cl2)n  than  to  Hinrichson's 
[(C10H16)2S2Cl2]n.  When  pure  Ceylon  para,  gutta-percha  and  ex- 
tracted and  purified  balata  are  treated  with  37  per  cent  of  sulfur  at 
135°  the  final  products  are  apparently  identical  and  correspond  to 
the  empirical  formula  (C10H16S2)n.81  In  the  ordinary  hot  process  of 
vulcanization,  using  about  10  per  cent  of  sulfur  the  first  stage  evi- 
dently consists  in  adsorption,  followed  by  slow  chemical  combination,82 
and  when  sulfur  chloride  is  employed  adsorption  followed  by  slow 
chemical  combination  appears  to  be  the  result.83 

Vulcanization  is  essentially  an  increase  in  the  degree  of  polymeri- 
zation of  the  rubber  and  when  this  is  effected  by  means  of  sulfur  or 
sulfur  chloride,  it  is  probable  that  combination  also  occurs  between 
sulfur  atoms  attached  to  different  complexes  or  molecules,  since  the  ten- 
dency of  sulfur  derivatives  to  polymerize  is  well  known,  as  for  example 
the  thio-aldehydes.  The  literature  on  the  subject  of  vulcanization  is 
voluminous,  and  is  burdened  by  much  speculative  matter  which  will 
not  be  reviewed  here;  the  subject  is  complex  and  the  effect  of  varia- 
tions in  mechanical  treatment,  and  the  presence  of  other  substances, 
is  often  very  marked.  These  effects  are  of  great  importance  to  the 
rubber  industry  but'  are  not  of  general  interest.  The  causes  of  the 
variability  of  the  vulcanization  of  plantation  Hevea  rubber  have  been 
particularly  well  investigated 8*  and  recently  a  large  number  of  sub- 
stances have  been  investigated  which  promote  further  polymerization 
independently  of  sulfur  or  which  greatly  accelerate  the  vulcanization 
when  sulfur  is  employed.  Thus  para  nitrosodimethylaniline,  one  of 
the  most  potent  accelerators,  when  added  in  amounts  equivalent  to 
0.33  to  0.5  per  cent,  reduces  the  time  required  for  vulcanization  to 
about  one-third  that  normally  required  and  the  proportion  of  sulfur 
may  also  be  somewhat  reduced.  That  many  mineral  substances, 
such  as  litharge,  red  lead,  zinc  oxide,  magnesium  oxide,  etc.,  accelerate 
vulcanization  by  sulfur  has  long  been  known  but  a  large  number  and 
variety  of  organic  substances  also  function  in  this  manner.  A  large 
number  of  aromatic  nitro  derivatives,  piperidine  and  quinoline  and 

"Peachey,  J.  8oc.  Chem.  Ind.  31,  1103   (1909). 
8°Kirchof,  Kolloid  Z.  14,  35   (1914). 

81  Spence  and  Young,  Kolloid  Z.  13,  265    (1913). 

82  Harries,  Ber.  1,9,  1196  (1916). 

13  Hinrichson,  Chem.  Abs.  12,  104  (1918)  ;  van  Rossem,  CTiem.  Aba.  12,  2142  (1918). 
"Eaton  &  Grantham,  J.  Soc.  Chem.  Ind.  S^  989  (1915). 


THE  ETHYLENE  BOND  137 

their  derivatives,  amines  and  substituted  amines  and  ureas,  have  been 
found  to  have  accelerating  effects.85  Barium  peroxide  alone  has  no 
vulcanizing  effect  but  benzoyl  peroxide  does  "vulcanize"  in  the  absence 
of  sulfur 86  but  the  product  is  markedly  different  from  the  commercial 
products  made  by  the  use  of  sulfur  or  sulfur  chloride.87  Dubosc  has 
insisted  that  colloidal  sulfur,  which  he  assumes  is  formed  by  the  inter- 
action of  hydrogen  sulfide  and  sulfur  dioxide,  produced  in  situ  during 
vulcanization,  is  solely  responsible  for  the  vulcanization  effects.  This 
opinion  is  not  commonly  held  but  it  is  of  interest  in  view  of  the  fact 
that  a  process  of  cold  vulcanizing  has  recently  come  into  use  which 
consists  in  treating  rubber  with  a  mixture  of  these  two  gases,  sulfur 
being  formed  in  an  extremely  finely  divided  state.  Reychler 88  showed 
that  rubber  takes  up  nearly  25  times  as  much  sulfur  dioxide  as  C02, 
under  comparable  conditions,  and  Peachey  89  has  taken  advantage  of 
this  fact  in  his  process  of  vulcanization  just  alluded  to. 

The  saturation  of  the  double  bonds  in  rubber  by  sulfur  explains 
the  value  of  "hard  rubber"  in  handling  hydrochloric,  hydrofluoric 
and  other  acids.  The  action  of  sulfuric  or  other  mineral  acids  upon 
unvulcanized  rubber  has  been  but  very  little  investigated. 

Addition  of  Ozone. 

That  ozone  is  capable  of  reacting  with  unsaturated  hydrocarbons 
has  been  known  for  many  years,  the  reaction  of  ethylene  and  ozone 
to  form  formaldehyde,  formic  acid  and  carbon  dioxide  having  been 
noted  by  Schoenbein  ;90  also  the  reaction  between  benzene  and  ozone 
was  studied  by  Houzeau  and  Renard 91  but  the  reaction  product  was 
regarded  as  a  peroxide  rather  than  an  ozonide.  The  true  character 
of  these  reactions  was  first  made  clear  by  Harries,  who  pointed  out 
that  reaction  with  ozone  in  the  absence  of  moisture  gave  thick  viscous 
substances,  which  were  very  explosive,  but  which  he  was  able  to  show 
by  analysis  consisted  of  products  containing  03  for  each  double  bond 
present  in  the  original  substances.  These  ozonides  can  break  down 
in  two  ways  as  follows, — 

1 — By  reaction  with  water  to  form  hydrogen  peroxide  and  ketones 
or  aldehydes  accompanied  by  complete  rupture  of  the  double  bond. 

88  Twiss,  J.  Soc.  Chem.  Ind.  36,  782  (1917)  ;  King,  Met.  &  CJiem.  Eng.  15,  231 
(1916). 

88  Ostromuislenski,  J.  Russ.  tf,  1462    (1915). 

87  Twiss,  loc.  cit. 

88  J.  chim.  phys.  8,  617    (1910). 

89  Peachey  &  Shipsey,  J.  Soc.  Chem.  Ind.  1921,  4  T. 
80  J.  prakt.  Chem.  66,  282  (1855). 

91Compt.  rend.  76,  572    (1873). 


138      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 
>C C<  +  H20 >>CO  +  OC<  +  HA 


2  —  Decomposition  can  take  place  on  warming  or  in  solvents  such  as 
absolute  alcohol  or  glacial  acetic  acid  in  the  absence  of  water  to  give 
a  peroxide  and  a  ketone  or  aldehyde. 

0 
>C  —     -  C<  ---  »C<  I  +  OC< 


The  peroxides  formed  as  in  equation  (2)  can  often  react  with  water 
to  form  a  carboxylic  acid;  for  example,  mesityl  oxide  ozonide  breaks 
down  in  accordance  with  the  two  schemes  just  shown  as  follows: 
(a) 


(CH3)2C 


CH.CO.CH 


| 
—  0  —  0 


H,0 


(CH3)  2CO  +  OCH  .  CO  .  CH, 


(b) 
(CH3)2C 


CH.CO.CH3->  (CH3)2CO      0 


0  —  0  — 


|>CH.CO.CH, 
0 


(bj 
0 

0 

Decomposition  according  to   (b)   and   (b±)   accounts  for  the  fact 
that  the  yield  of  methylglyoxal  is  relatively  small  and  formic  and 


CH3 


ho"t~-» 


pulegone  ozonide 


p-methyl- 
adipic  acid 


1-methylcyclo- 
hexanedione-(8,  4) 


THE  ETHYLENE  BOND 


139 


acetic  acids  are  formed.  %  This  type  of  decomposition  accounts  for  re- 
actions which  were  for  a  time  considered  abnormal,  for  example, — 
pulegone  ozonide  92  yields  (3-methyladipic  acid  and  not  the  substance 
which  would  be  expected  from  the  character  of  the  great  majority  of 
ozonide  decompositions,  namely,  1-methylcyclohexanedione-  (3, 4) 

Similarly  camphene  gives  a  little  camphenilone  and  a  relatively 
large  yield  of  a  lactone,  whose  formation  is  attended  by  rupture  of  the 
six  carbon  ring.93 


HCHO 


Harries  regards  these  peroxides  formed  by  the  decomposition  of 
ozonides  as  having  the  constitutions  indicated  in  the  above  examples. 
Another  type  of  peroxide  is  formed  by  the  direct  action  of  ozone  upon 
carbonyl  derivatives,  aldehydes  or  ketones,  thus  nonyl  aldehyde  acted 
upon  by  ozone  forms  a  labil  peroxide  melting  at  about  10°,  but  a  more 
stable  peroxide  of  the  same  empirical  formula  CH3.  (CH2)7.CH02  is 
formed  by  the  decomposition  of  the  ozonides  of  substances  containing 
the  group  CH3(CH2)7CH  =  CHR.  This  more  stable  peroxide  melts 
at  73°  and  can  readily  be  recrystallized. 

The  reaction  of  ethylene  bonds  with  ozone  is  substantially  as  gen- 
eral a  reaction  as  is  the  reaction  of  bromine.  In  fact,  ozone  reacts  with 
many  substances,  which  are  commonly  regarded  as  not  having  unsatu- 
rated  bonds  of  the  ethylene  type,  for  example,  benzene  and  naphtha- 
lene. It  is  of  interest  to  note  that  the  ethylene  bond  in  fumaric  acid, 
which  substance  is  not  hydrated  by  sulfuric  acid,  reacts  only  very 
slowly  with  ozone,  but  when  prepared  by  employing  very  concentrated 
ozone  the  ozonide  spontaneously  decomposes  on  standing,  yielding  the 
original  substance,  fumaric  acid.  This  reaction,  which  has  been  em- 
ployed so  successfully  by  Harries  in  the  investigation  of  various  kinds 
of  caoutchouc,  has  been  an  outgrowth  of  his  studies  of  the  reaction 
of  ozone  upon  mesytilene,  amylene,  2 . 6-dimethylheptadiene- (2, 5), 
diallyl,  and  similar  substances.  In  this  connection,  it  should  be  men- 
tioned that  conjugated  dienes  react  very  energetically  with  ozone  to 

K  Harries,  Ann.  374,  297  (1910). 

M  Semmler,  Ber.  Jfi,  246  (1909)  ;  Palmen,  Ber.  *S,  1432  (1910). 


140      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

form  mono-ozonides,  but  the  diozonides  are  formed  only  very  slowly. 
Diallyl,  or  1, 5  hexadiene,  in  chloroform  solution  readily  gives  a  very 
explosive  syrupy  diozonide,  which  on  hydrolysis  yields  succinic  dialde- 
hyde  and  formaldehyde. 

A 

CH2CH  =  CH2          CH2CH CH2          CH2CHO 

>  I  >  I  +2HCHO 

r^TT  r^Ti       r^Ti             /^TJ  r^tr  r^tr  OTJ  r^~crr\ 

U±12L/±1  =•  O±12  O±19O±1 Oxlo  Ly±l9OilU 

V 

o3 

Geometrical  isomers  of  the  type  of  fumaric  and  maleic  acids  yield 
identical  ozonides  or  rather  identical  hydrolytic  products,  which  fact 
may  serve  to  establish  the  structural  similarity  of  such  isomers. 

The  work  of  Harries  on  the  constitution  of  certain  unsaturated 
hydrocarbons  has  clearly  shown  that  most  of  them  are  in  reality  mix- 
tures of  isomers,  a  fact  brought  out  in  the  section  on  the  preparation 
of  unsaturated  hydrocarbons.  Thus  the  octadiene  made  by  the  action 
of  methyl-magnesium  iodide  on  succinicdiethyl  ester  and  decompo- 
sition of  the  resulting  glycol  or  its  bromide  was  supposed  to  have  the 
constitution,—  (CH3)2C  =  CH.CH  =C(CH3)2  but  the  ozone  method 
clearly  shows  that  this  hydrocarbon  is  in  reality  a  mixture  chiefly  con- 

CH2  CH2 

sisting  of  the  hydrocarbon  C.CH2  —  CH2  —  C  (2.5  di- 

CH3  CH3 

methylhexadiene —  (1.5)  ). 

When  the  alkaloid  pseudo-pelletierin  is  decomposed  by  the  method 
of  exhaustive  methylation,  the  basic  nitrogen  atom  is  removed  and  a 
cyclo-octadiene  results  which  Willstatter  and  Veraguth 94  were  inclined 
to  regard  as  containing  a  pair  of  conjugated  double  bonds.  Their 
cyclo-octadiene  polymerized  with  remarkable  ease.  Nevertheless,  Har- 
ries showed  that  this  hydrocarbon  forms  a  diozonide  which  is  hydro- 
lyzed  normally  yielding  succinic  dialdehyde,  and  succinic  acid,  indi- 
cating that  the  hydrocarbon  is  cyclo-octadiene — (1.5). 
CH2-  -CH2— CH2  CH^CH  — CH2 

CH2     HO .  N  (CH3)  2  CH2 >  CH2  CH2 


CH2 


CH2 CH,  CH,—  CH  =  CH 


"Ber.  38,  1975  (1905)  ;  40,  959   (1907). 


THE  ETHYLENE  BOND  141 

A 

CH2  —  CH CH  —  CH2  CH2  —  CHO 

I  |  2    | 

>     CH9- 


CHO 
H2  — CH CH  — CH, 

v 

03 

Harries  has  summarized  his  researches  on  ozonides  in  four  general 
articles.95  Some  of  the  ozonides  first  prepared  by  Harries  in  the  earlier 
period  of  his  researches  were  not  pure  and  consisted  apparently  of 
mixtures  derived  by  the  addition  of  03  and  also  the  hypothetical  com- 
pound 04  or  oxozone.  After  passing  the  crude  ozone-oxygen  mixture 
through  5  per  cent  caustic  soda  and  then  through  sulfuric  acid,  the  gas 
then  gave  pure  ozonides.  Polymeric  forms  of  ozonides  have  frequently 
been  noted,  an  oily  volatile  monomolecular  form  having  usually  a 
sharp  disagreeable  odor,  and  polymers  in  the  form  of  solid  gummy, 
glassy  or  crystalline  substances  having  little  or  no  odor,  usually  being 
observed.  Thus  monomolecular  butylene  ozonide  can  be  distilled  in 
vacuo  and  it  readily  dissolves  in  the  common  solvents.  The  dimeric 
form  of  butylene  ozonide,  however,  is  an  almost  odorless  gummy  sub- 
stance very  sparingly  soluble  in  water.  Formation  of  ozonides  at  low 
temperatures,  below  0°,  favors  larger  proportions  of  the  polymeric 
forms. 

Unsaturated  cyclic  hydrocarbons  behave  toward  ozone  and  sub- 
sequent hydrolysis  generally  like  aliphatic  defines.  Cyclopentene 
ozonide,  C5H803,  is  soluble-  in  the  common  solvents  and  is  smoothly 
hydrolyzed  by  water  resulting  chiefly  in  the  mono-aldehyde  corre- 
sponding to  glutaric  acid, 


CH2  — CH 

)CH— > 
H2  — CH2 

CH2  — CH-- 0  — 0 

..\ I....  CH2  — COOH 

\CH  —  0 >  CH2  —  CH2  —  CHO 

CH2  — CH2 

MAnn.  Stf,  311   (1905)  ;  374,  288   (1910)  ;  S90,  236   (1912)  ;  W,  1   (1915). 


142      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

Cyclohexene  ozonide  is  much  more  stable  to  water  but  on  long  boil- 
ing yields  hexane  dialdehyde  and  adipic  acid.  Limonene  readily  yields 
a  mono-ozonide,  the  isopropenyl  side  chain  96  first  being  reacted  upon, 
and  at  a  much  slower  rate  the  cyclic  double  bond  is  attacked.97 

By  the  ozonization  of  natural  Hevea  rubber,  Harries  obtained  lae- 
vulinic  acid  and  laevulinic  aldehyde,98  from  which  observation  he 
concluded  that  Hevea  rubber  is  a  polymer  of  the  di-isoprene,  1.5- 
dimethy  1  cy  clo-octadiene-  (1.5), 

=  C(CH3).CH2 


CH2C  =  CH  -  CH 


CH5 


However,  the  real  unit,  which  is  polymerized  to  ring  complexes  an 
unknown  number  of  times,  is  the  group  —  CH2C(CH3)  =  CH.CH2  — . 
Artificial  isoprene  rubber,  on  treating  with  ozone  and  subsequent  hy- 
drolysis, yields  succinic  acid  and  acetonylacetone  in  addition  to  lae- 
vulinic acid  and  aldehyde,99  which  products  could  conceivably  be  de- 
rived from  1 . 6-dimethy  Icy  clo-octadiene-  (1 . 5) . 

The  first  work  upon  the  treatment  of  petroleum  distillates  with 
ozone  appears  to  have  been  done  by  Molinari  and  Fenaroli,100  who  ob- 
tained a  yield  of  32  per  cent  of  an  ozonide  from  a  kerosene  fraction, 
boiling  at  295°-300°,  derived  from  a  Russian  petroleum.  The  subject 
has  not  been  pursued  further  but  inasmuch  as  Harries  observed  that 
refined  petroleum  ether  and  hexane  are  not  altogether  unacted  upon 
by  ozone  when  used  as  solvents  for  unsaturated  substances,  the  con- 
clusions of  Molinari  that  a  conjugated  di-olefine,  C17H30,  was  present 
in  the  relatively  large  proportions  indicated  by  the  yield  stated,  are 
hardly  to  be  accepted.  Ethane  is  reacted  upon  by  dilute  ozone  at 
100°,  the  initial  oxidation  products  being  ethyl  alcohol  and  acetalde- 
hyde.101  During  the  recent  war  period  Harries  turned  his  attention 

96  Prior   to  the   researches   of   Harries,   vanillin   had   been   made  by   the  action   of 
ozone  on  iso-eugenol.      (Otto,  Ann.  d.  Chim.  &  Phys.   [7]  13,  120   [1898]  ;  German  Pat. 
97,  620.)      Better  yields  were,  for  a  time,  obtained  by  using  crude  ozonizing  apparatus 
giving  dilute  ozone,    about   1%,   than   when   using   more   concentrated   ozone   made    by 
improved    apparatus.     Harries    later    showed    that    70%    yields   could    be   obtained    by 
treating  the  ozonide  with   zinc  dust  and  acetic  acid    (Ber.   48,  32    [1915].)      The   side 
chain  in  safrol  also  reacts  readily,  Semmler  and  Bartlett  (Ber.  Jtl,  2751  [1908]),  obtain- 
ing homopiperonylic  aldehyde. 

97  Critical  examination  of  Harries'  work  is  apt  to  elicit  the  fact  that  he  frequently 
paid  little  attention   to  the  history  or  purity  of  his  original  material  and   also   that 
more  definite  results   might  often   have   been   obtained,  in   the  terpene   series,   in   the 
hands  of  other  well-known  specialists  in  this  field. 

»*Ber.  38,  1195,  3986  (1905)  ;  46,  733   (1913)  ;  Ann.  406,  173  (1914). 
"Steimmig,  B&r.  47,  350   (1914). 

100  Ber.  41,  3704    (1908). 

101  Bone  and  Drugman,  Proc.  Chem.  Soc.  20,  127  (1904). 


THE  ETHYLENE  BOND  143 

to  the  oxidation  by  ozone  of  the  highly  unsaturated  oily  distillates 
obtained  by  the  low  temperature  carbonization  of  lignite.  Although 
the  method  had  a  large  scale  trial  in  Germany  during  the  stress  of 
conditions  imposed  by  the  war,  the  yields  of  fatty  acids  obtained  were 
very  small  and  the  project  was  soon  abandoned.102  Harries  identified 
stearic,  palmitic  and  myristic  acids  among  the  reaction  products,  to- 
gether with  relatively  large  proportions  of  simpler,  water  soluble  acids, 
including  formic,  acetic,  propionic  and  oxalic  acids. 

The  reaction  of  unsaturated  hydrocarbons  with  sulfur  trioxide  is 
naturally  a  very  energetic  one  leading,  under  ordinary  experimental 
conditions,  to  oxidation  of  the  hydrocarbon  and  formation  of  S02.  A 
definite  reaction  product  is  easily  obtainable  with  ethylene,  the  crystal- 
line anhydride  carbyl  sulfate  being  formed. 

CH2  CH2-S02\ 

||      +2S03 >|  >0 

CH2  CH2  —  0-S02 

No  further  work  on  this  reaction  seems  to  have  been  done  since  its 
discovery  in  1838  103  and  whether  ethylene  homologues  can  form  similar 
derivatives  (at  low  temperatures  in  a  neutral  solvent)  is  not  known. 
The  anhydride  carbyl  sulfate  reacts  energetically  with  water10*  to 

CH2.S03H 
form  ethionic  acid,    I  which   substance   is   then   rapidly 

CH,.O.S03H 

CH2.S03H. 
hydrolyzed  to  iso-ethionic  acid  Sulfonic  acid  groups  in 

CH2.OH 

which  sulfur  is  bound  directly  to  carbon,  as  in  iso-ethionic  acid,  are 
not  easily  displaced  and  alcohols  or  glycols  cannot  be  made  from  them 
by  any  known  methods. 

The  propane  derivative,  propanol-(l)  sulfonic  acid- (3),  is  formed 
when  allyl  alcohol  reacts  with  an  alkali  bisulfite, 

CH2OH.  CH2OH. 

CH          +  KHS03 »  CH2 

CH2  CH2.S03K. 

102  Ozone,  as  an  oxidizing  agent  to  be  employed  in  industrial  operations,  Is  usually 
much  too  costly  compared  with  other  methods  of  oxidation,  although  its  cost  may  be 
expressed  largely  in  terms  of  the  cost  of  electrical  power. 

103  Regnault,  Ann.  25,  32   (1838)  ;  Magnus,  Pogg.  Ann.  47,  509  (1839). 
'"Claesson,  J.  prakt.  Chem.   (2),  19,  253  (1879). 


144      CHEMISTRY  OF  THE  NON-BENZEN01D  HYDROCARBONS 

The  behavior  of  ethylene  bonds  to  sulfur  dioxide  and  aqueous  sul- 
furous  acid  is  very  different  from  sulfuric  acid  in  that  hydration  to  alco- 
hols does  not  occur,  but  addition  to  form  very  stable  sulfonic  acids  is 
frequently  the  result.  This  reaction  follows  the  general  rule  that  other 
adjacent  groups  exert  a  very  great  influence  upon  the  reactivity  of  the 
unsaturated  bond.  Anhydrous  sulfur  dioxide  has  not  been  shown  to 
react  with  unsaturated  hydrocarbons,  although  the  very  marked  solu- 
bility of  such  hydrocarbons  in  liquid  sulfur  dioxide  and  the  complete- 
ness with  which  they  may  be  extracted  from  paraffine  hydrocarbon 
mixtures,  as  in  the  Edeleanu  refining  process,  might  be  considered  as 
an  indication  of  the  formation  of  such  labil  compounds.  When  solu- 
tions of  amylenes  or  butylene  in  sulfur  dioxide  are  subjected  to  the 
action  of  heat  and  light,  amorphous  hornlike  solids  are  formed,105  the 
butylene  compound  having  the  composition  (C4H8S02)n,  and  when  the 
conjugated  diene,  isoprene,  is  allowed  to  stand  two  days  in  liquid 
sulfur  dioxide  a  crystalline  substance  C5H8S02,  is  formed.106 

Sulfonic  acid  derivatives  of  sabinene,  sabinol  and  pulegone  are 
formed  when  S02  is  passed  into  their  cooled  alcoholic  solutions  107  but 
the  formation  of  sulfonic  acid  derivatives  has  been  most  frequently  ob- 
served in  cases  where  the  ethylene  bond  is  adjacent  to  a  carbonyl 
group,  >CH  =  CH  —  C  —  .  Thus  acrolein  108  and  crotonic  aide- 


hyde  109  react  with  sodium  bisulfite  normally  so  far  as  the  aldehyde 
group  is  concerned  but  the  ethylene  bonds  react  also,  to  form  stable 
sulfonic  acid  derivatives,  which  are  not  affected  by  treating  with  alkali. 
The  aldehyde  group  generally  reacts  more  readily  with  bisulfite  than 
the  ethylene  bond  and  advantage  is  taken  of  this  fact  in  isolating  un- 
saturated aldehydes,  such  as  citral  and  citronellal,  from  mixtures 
containing  them.  Citral  contains  two  double  bonds,  one  of  them  adja- 
cent to  the  aldehyde  group,  and  both  ethylene  bonds  may  react  yield- 
ing the  stable  disulfonic  acid  salt,  C9H1T.  (S03Na)2.CHO,  from  which 
citral  cannot  be  regenerated.  When  cold  neutral  sodium  sulfite  is  em- 
ployed and  the  alkali,  formed  by  the  reaction,  is  neutralized  as  fast 
as  formed, 

C9H15.CHO  +  2Na2S03  +  2H20  -*  C9H15(S03Na)2CHO  +  2NaOH 

10BMathews  and  Elder,  J.  8oc.  Chem.  Ind.  1915,  670. 

10«de  Bruin,  Chem.  A  6s.  9t  623  (1915). 

1OT  Wallach,  Nachr.  Wiss.  Ges.  Goettingen.  1919t  321. 

"»Muller,  Ber.  6,  1442    (1873). 

"•Haubner,  Monatsh.  12,  546  (1891). 


THE  ETHYLENE  BOND  145 

then  an  unstable  dihydrosulfonate  is  formed  from  which  citral  is  easily 
regenerated.110  Citronellal  contains  only  one  double  bond  and  this  is 
far  removed  from  the  aldehyde  group  and  accordingly  less  reactive. 
Under  the  conditions  just  described  citronellal  is  not  reactive;111  with 
cold  concentrated  bisulfite,  in  the  presence  of  sodium  bicarbonate,  the 
aldehyde  group  only  reacts,  and  normally,  but  when  warmed  with  an 
excess  of  bisulfite  (containing  a  little  sulfite)  the  stable  sulfonate  is 
formed.112 

CH3\  OH 

C  =  CH.CH2CH2CH.CH2CH< 

I,H  oso*Na 

citronellal 

\     CH3sx  OH 

hot  \  _  CH2  CH2CH2CH  .  CH2CH  < 


/  1  I  OS02Na 

S03Na  CH3 

cannot  be  regenerated. 

Nitrosyl  chloride  has  been  a  most  useful  reagent  in  the  investiga- 
tion of  the  terpenes  but  has  not  been  used  in  the  investigation  of 
unsaturated  hydrocarbons  derived  from  petroleum,  although  the 
first  thorough  study  of  the  addition  of  nitrosyl  chloride  to  defines 
was  carried  out  with  amylene.113  When  Wallach  first  undertook  the 
study  of  the  terpenes  the  literature  had  become  confused  with  a  va- 
riety of  names  for  hydrocarbons  which  were  not  clearly  differentiated, 
one  from  another,  and  the  names  adopted  usually  referred  to  various 
particular  sources.  The  reaction  with  nitrosyl  chloride,  which  had 
been  discovered  by  Tilden  and  Shenstone,114  proved  to  be  a  most 
valuable  reagent  for  the  preparation  of  characteristic  crystalline  de- 
rivatives of  these  unsaturated  hydrocarbons  and  the  multiplicity  of 
names  began  to  diminish  as  the  identity  of  differently  named  terpenes 
was  established.  The  addition  products  formed  by  the  reaction  of 
these  hydrocarbons  with  nitrogen  trioxide  and  nitrogen  tetroxide  also 
proved  useful  in  this  connection.  Crystalline  tetrabromides,  dihydro- 
chlorides,  etc.,  also  assisted  in  this  work  of  identification  and  "cit- 
rene,"  "hesperidene,"  and  "carvene,"  for  example,  were  shown  to  be 
identical  and  are  known  as  limonene. 

110Tiemann,  Her.  SI,  3306,  3315   (1898). 
mTiemann,  B&r.  S2,  816,  818   (1899). 
112Tiemann,  Ber.  SI,  3306  (1898). 
118  Wallach,  Ann.  245,  246   (1888). 
114  J.  Chem.  Soc.  1877,  I,  554. 


146      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

Among  the  simpler  olefines  the  ability  of  defines  to  combine  with 
nitrosyl  chloride  increases  with  molecular  weight  (or  introduction  of 
the  "positive"  methyl  groups) :  ethylene  forms  only  ethylene  chloride, 
and  propylene  forms  both  the  dichloride  and  nitrosochloride.115  As 
indicating  the  variety  of  ethylene  types  which  form  nitrosochlorides, 
the  following  may  be  mentioned,  trimethyl  and  tetramethyl  ethyl- 
ene, cyclohexene,  methene  derivatives  R2C  =  CH2,  and  also  hy- 
drocarbons having  a  semicyclic  double  bond  and  a  side  chain,  as 

CH2 
(CH2)X<         >C  =  CH.R.     Unsaturated  hydrocarbons  having  the 

CH2 

groups  >C  =  CH2,  and  —  CH  •=  CH2,  do  not  usually  yield  crystalline 
nitrosochlorides:  116  the  type  R2C  =  CHR  usually  does  yield  crystal- 
line nitrosochlorides.117  The  terpene,  (5-fenchene 


forms  a  crystalline  nitrosochloride  and  Wallach  has  obtained  such 
crystalline  derivatives  from  other  hydrocarbons  whose  double  bond 
is  similarly  situated.118 

The  crystalline  nitrosochlorides,  nitrosites  and  nitrosates  are  gen- 
erally bimolecular 119  and  hence  called  bis-nitrosochlorides,  6is-nitro- 
sites  and  fo's-nitrosates,  but  in  solution  many  12°  of  these  derivatives 
are  blue  in  color  and  are  monomolecular.  Many  of  the  nitrosochlorides, 
in  monomolecular  form,  are  volatile  with  steam  without  decomposition ; 
for  example,  the  blue  modifications  derived  from  the  hydrocar- 
bons,121- 122 

""Tilden  &  SudbVough,  J.  Chem.  Soc.  63,  479   (1893). 

"•Meyer,  "Analyse  &  Konstitutioniren.  org.  Verb,"  Ed.  2,  Berlin,  1909,  p.  939. 

11TWeyl,  "Die  Methoden  d.  org.  Chemie,"   II,  639    (1911). 

118  Awn.  Slil,  322   (1906)  ;  865,  267   (1909). 

118Baeyer,  Ber.  28,  641,  650,  1586   (1895)  ;  29,  1078   (1896). 

120  Wallach  &   Sieverts,  Ann.  S06,  279    (1898),  332,  309    (1904),  showed  that  pinol 
nitrosochloride  may  exist  in  a  colorless  monomolecular  form. 

121  Wallach,  Ann.  353,  308   (1907)  ;  396,  280. 

122  The  preparation  of  nitrosochlorides  is  best  carried  out  by  dissolving  the  hydro- 
carbon in  an  equal  volume  of  glacial  acetic  acid,   adding  one  volume  of  ethyl  nitrite, 
cooling  to   10°,   and  then   adding  one-third   volume   of   concentrated   hydrochloric  acid. 
In  most  cases,  where  a  crystalline  nitrosochloride  is  possible,  an  abundant  crystalline 
deposit  of  the  nitrosochloride  forms  in  a  few  minutes.     Acetone  is  generally  the  best 
solvent  for  recrystallizing  these  derivatives.     Nitrosobromides  are  also  easily  prepared 
but   are   less   stable    than    the   corresponding   chlorides :    5CC    tetramethyl-ethylene   and 
5CC  ethyl  nitrite,  cooled  to  0°  C  and  treated  with  5CC  concentrated  HBr  solidifies  in  a 
few  minutes  to  the  solid  bisnitrosobromide. 


THE  ETHYLENE  BOND  147 


=C(CHJ. 


The  value  of  the  nitrosochlorides  has  been  chiefly  their  ready  con- 
version to  oximes,  from  which  ketones  may  be  made,  and  to  other 
more  stable  substances  suitable  for  identification  purposes,  for  example, 
condensation  with  benzylamine.  All  three  types  of  nitroso  derivatives 
may  be  converted  into  the  isomeric  oximes  by  carefully  warming  with 
alkalies, 

(CH3)2C-C1  (CH3)2C.C1 

CH-CH.NO  *  CH3-C  =  N. 


3 


It  has  been  proposed  to  utilize  the  reaction  with  nitrogen  tetroxide 
in  determining  the  constitution  of  defines,  since  the  addition  product 
RCH.N02.CHN02.R,  is  split  by  heating  with  concentrated  hydro- 
chloric acid  to  give  fatty  acids.123 

Ammonia  and  aliphatic  amines  react  with  the  ethylene  bond  in  cer- 
tain instances  where  the  very  reactive  ethylene-carbonyl  group 
>CH  =  CH  —  C  —  occurs,  as  in  mesityl  oxide,124 


(CH3)2C  =  CH.CO.CH3  +  NH3 


CH2COCH3 


Vinyl  chloride,  which  polymerizes  on  GtapHin*  but.  is  nnite  stable  to 
sulfuric  acid,  reacts  with  ammonia  to  give  ethylenediamine,125 

CH2  =  CHC1  +  2NH3  -    ^NH2 .  CH2CH2NH2HC1 

The  unsaturated  hydrocarbons  themselves  are  not  reactive  to  am- 
monia or  amines.  The  ethylene-carbonyl  group  is  also  reactive  to 
hydroxylamine  in  a  fairly  large  number  of  substances.  Allyl  ketones, 
CH2  =  CH .  CH2COR,  react  normally  to  give  oximes  but  the  ethylene 
bonds  in  propenyl  and  vinyl  ketones  also  react,126 

123  Jegorow,  J.  prakt.  Chem.  S6,  521   (1912). 

12*  Sokoloff,  Ber.  7,  1387   (1874)  ;  Kohn,  Monatsh.  25,  135   (1903)  ;  Blaise  &  Maire, 
Compt.  rend.  142f  215   (1906). 

125Engel,  Compt.  rend.  Wk,  1621   (1887). 

128  Blaise,  Compt.  rend.  138,  1106  (1904)  ;  1J,2,  215   (1906). 


148      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

R 
CH2  =  CH .  COR  -        -4  NH .  OH .  CH2CH2C 

N.OH 

The  ethylene-carbonyl  group  also  reacts  with  aniline,  phenyl  hydra- 
zine,  urea,  semicarbazide,  mercaptans,  hydrogen  sulfide,  hydrocyanic 
acid,  malonic  and  acetoacetic  esters. 


C02R  C02R 

aniline  127  +  RCH  =  C< >  RCH  —  CH< 

C02R  I  C02R 

NH.C6H5 

CH.COOH  NH  — CO  — CH2 

ureal28+\\  >| 

CH2  CO  — NH  — CH2 

semicarbazide  129  +  (CH3)2C  =  CHCOCH3 

CH3 

>  (CH3)2C  — CH2.C  =  N.NH.CO.NH2 


NH.CO.NH.NH2 

ethyl  mercaptan  13°  +  (CH3)2C  =  CH.CO 

CHS 
SC2H5 

SC2H5 


hydrogen  sulfide  131  +  carvone >  (C40H140)2H2S 

hydrocyanic  acid  132  +  (CH3)2C  =  CH.COCH3 
-->(CH3)2C  — CH2COCH3 

CN 

»«  Blank,  Ber.  28,  145    (1895). 

128  Fischer  &  Roeder,  Ber.  8Jh  3751    (1901). 

129  Important  in  connection  with  the  use  of  semicarbazld  for  the  identification  of 
such  ketones ;  citronellal  and  two  molecules  of  semicarbazid  gives  the  crystalline  semi- 
carbazino-semicarbazone    immediately.     Cf.    Rupe,    Ber.    86,    4377     (1903)  ;     Semmler, 
B&r.  1^1,  3991    (1908). 

»°Posner,  Ber.  85,  799   (1902)  ;  37,  502   (1904). 

181  Cf.  Wallach,  Ann.  279,  385   (1894)  ;  31,3,  32   (1905)  ;  mesityloxide  and  the  hydro- 
carbon menthene  also  form  compounds  with  H2S. 

182  Lap  worth,  Jour.  CTiem.  Soc.  85,  1214    (1904). 


THE  ETHYLENE  BOND  149 

acetoacetic  ester 133  +  CH2  =  CH.C02R 
CH3COCH.C02R 

CH2  — CH2.C02R 

The  above  reactions  cannot  be  said  to  be  general  reactions  even 
for  a,  (3-unsaturated  ketones  or  acids  (the  "ethylene-ketone"  group), 
and  none  of  them  have  so  far  been  found  applicable  to  hydrocarbons. 
In  fact,  until  the  mechanism  of  such  reactions,  and  the  part  played  by 
the  carbonyl  group,  is  understood,  it  is  questionable  whether  this  last 
group  of  reactions  should  really  be  considered  as  reactions  of  the  un- 
saturated  bond ;  it  would  be  more  correct  to  consider  them  as  reactions 
of  the>CH  =  CH  —  C  —  or  "ethylene-carbonyl"  group.  These  con- 


siderations  apply  also  to  the  hydrolytic  rupture  of  the  ethylene  bond  of 
this  group  which  is  noted  when  many  substances,  for  example,  mesityl 
oxide,  citral 134  and  pulegone,  are  treated  with  dilute  alkalies  or  min- 
eral acids,  thus 

+  H20 
(CH3)2C  =  CH.CO.CH3 »  (CH3)2CO  +  CH.COCH3 


(CH3)2C  =  CH.CH2CH2C  =  CH.CHO 

CH, 

citral 
+  H20 
»  (CH3)2C  =  CH.CH2CH2C  =  O 

CH3 
+  CH3CHO 

Metallic  sodium  has  been  observed  to  combine  directly  with  un- 
saturated  hydrocarbons  135  only  in  a  few  cases  where  a  negative  group 
is  present,  as  in  stilbene,  C6H5CH  =  CH2.  Metallic  sodium  in  a  very 
finely  divided  or  colloidal  form  is  employed  for  the  purpose. 

Preparation  of  defines. 

As  regards  the  preparation  of  olefine  hydrocarbons,  it  may  be 
pointed  out  that  most  methods  of  preparation  yield  a  mixture  of  isomers 

183  Vorlander,  Ann.  £94,  317   (1897). 

ls*Verley,  Bull.  soc.  chim.  (3),  17,  175  (1897).  Effected  best  by  heating  with 
potassium  carbonate ;  pulegone  may  be  hydrolyzed  by  heating  with  water  in  an  auto- 
clave. Wallach,  Ber.  32,  3388  (1899). 

""Schlenk,  Appenrodt,  Michael  &  Thai,  Ber.  )ft,  473  (1914). 


150      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

and  that  often  when  a  single  product  is  theoretically  probable  a  mix- 
ture of  isomers  results  owing  to  rearrangement.  Thus  Eltekow  136 
showed  that  isobutyl  alcohol  or  the  corresponding  halides  decompose 
to  give  a  mixture  of  three  butylenes, 

CH3  CH3 

>CH.CH2X  --  > 
CH3  CH3 


CH3CH2CH  =  CH2 

Haber  m  showed  that  on  heating  normal  hexane  to  600°  to  800°,  it  is 
decomposed,  methane  and  amylene  being  found  among  the  products 
formed  and  assumed  that  the  amylqne  was  alpha  amylene,  as  expressed 
by  the  equation, 

C3H7  .  CH2CH2CH3  --  >  C3H7CH  =  CH2  -f-  CH4 

But,  as  indicated  in  the  case  of  the  butylenes,  olefines  of  the  type 
RCH  =  CH2  are  prone  to  rearrangement  under  the  influence  of  heat. 

CH3 
Thus  the  amylene          >CH.CH  =  CH.,  rearranges  under  the  influ- 

CH3 
ence  of  heat,  or  mineral  acids,  to  trimethylethylene, 

CH3 

>C  =  CH.CH3 
CH3 

Noorduyn  138  has  made  a  study  of  the  constitution  of  the  olefines 
formed  by  heating  barium  fatty  acid  salts  with  sodium  ethoxide  or 
methoxide.  Very  little  work  of  this  kind,  critical  examination  of  the 
constitution  of  acyclic  olefines,  has  been  done.  Five  methods  have 
been  used  to  determine  the  constitution  of  unsaturated  substances. 

(1)  The  method  of  Varrentrap;  fusion  with  caustic  potash  which 
causes  a  change  of  position  of  the  double  bond  toward  the  carboxyl 
group  (of  fatty  acids). 

(2)  Oxidation  by  potassium  permanganate,  in  which  method  1:2 
glycols  are  former  as  intermediate  products. 

(3)  Beckmann's  transposition,  in  which  method  the  formation  of 
the  dibromide  is  the  first  step. 

™Ber.  13,  2404  (1880)  ;  Cf.  Nef,  Ann.  SIS,  1  (1901). 

m  Ber.  29,  2691    (1896). 

™Rec.  trav.  ch4m.  S8,  317   (1919). 


THE  ETHYLENE  BOND  151 

(4)  Jegorow's  method  based  upon  the  addition  of  N204  to  the 
double  bond. 

(5)  Harries'  method  consisting  in  reaction  with  ozone  and  hy- 
drolysis of  the  resulting  ozonide. 

Noorduyn  used  the  ozonide  method.  Examination  of  the  decylene 
made  by  heating  the  barium  salt  of  undecylenic  acid  with  sodium 
ethoxide  and  hydrolyzing  the  ozonide  of  the  hydrocarbon  yielded  for- 
maldehyde, acetic,  propionic,  butyric,  valeric  and  hexylic  acids  show- 
ing that  the  hydrocarbon  is  a  mixture  of  isomers.  Similarly  the  hepta- 
decylene,  from  oleic  and  elaidic  acids  and  sodium  methoxide  was  shown 
to  be  a  mixture  of  isomeric  hydrocarbons.  Nonylenic  acid,  from  oenan- 
thole  and  malonic  ester,  yielded  a  mixture  of  octylenes  and  "(3-octyl- 
ene,"  boiling-point  124°-126°  from  secondary  octyl  alcohol  was  also 
shown  to  be  a  mixture. 

Primary  alkyl  iodides  or  alcohols  invariably  yield  a  mixture  of  hy- 
drocarbons, as  a  critical  examination  of  the  physical  properties  of  the 
hydrocarbons  described  in  the  literature  as  having  been  prepared  in 
these  ways,  shows.  Thus  Morgan  and  Schorlemmer 139  prepared  a  hex- 
ene,  boiling-point  68°  to  70°,  from  a  monochlorohexane  and  Zelinsky 
and  Przewalski  14°  heated  n-hexyl  iodide  with  quinoline  and  obtained 
a  liquid  mixture  boiling  from  35°  to  67°.  On  oxidizing  the  fraction 
boiling  from  63.5°  to  65°  they  obtained  a  mixture  of  butyric  and 
valeric  acids  indicating  that  this  hexene  fraction  was  probably  a  mix- 
ture of  the  a  and  (3-isomers.  Van  Beresteyn 141  also  obtained  a  hexene 
boiling  at  67.7°  to  68.1°  by  decomposing  n-heptyl  alcohol  by  heating 
in  contact  with  nickel  at  220°. 

CH3  (CH2)  3CH2CH2CH2OH  -»  CH3  (CH2)  3CH  =  CH2  ?  +  CO  +  2H2 

However,  von  Braun  142  obtained  a  hexene,  by  gently  heating  n-hexyl 
trimethyl  ammonium  hydroxide,  which  showed  a  boiling-point  of  62° 
to  63°  and  which  he  regarded  as  a-hexene,  although  he  was  unable  to 
prove  the  constitution  of  it  on  account  of  the  small  quantity  made. 
Brooks  and  Humphrey  143  confirmed  the  character  of  von  Braun's 
a-hexene  by  synthesizing  it  by  means  of  a  reaction  which  had  been 
applied  by  Tiffeneau  144  to  the  synthesis  of  allyl  derivatives  of  ben- 

»»Ann.  m,  305    (1875). 

140  Ghent.  Zentr.  79,  II,  1854   (1908). 

141  Ibid.  1911,  II,   1017. 

142  Ann.  SSS,  22   (1911). 

143  J.  Am.  Chem.  Soc.  \0t  833  (1918). 
MCompt.  rend.  I39t  481  (1904). 


152      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

zene.145    They  treated  n-propyl  magnesium  bromide  with  allyl  bromide, 
the  reaction  taking  place  smoothly  at  room  temperature. 

C3H7MgBr  +  BrCH2CH  •=  CH2  —  >  C3H7CH2CH  =  CH2  +  MgBr 


2 


CH3 

Iso-a-heptene,          >CH.CH2CH2CH  =  CH2  and  iso-a-octene  were 
CH3 

also  made  in  a  similar  manner.  This  reaction  is  undoubtedly  appli- 
cable to  the  preparation  of  a  large  number  of  alpha  defines  of  this 
series. 

Pure  olefines  of  other  types  may  be  prepared  in  certain  cases  by 
making  use  of  the  symmetry  of  the  parent  alcohol  or  halide.  For  ex- 
ample, the  tertiary  alcohol  triethylcarbinol  readily  yields  pure  y-ethyl- 
(3-pentene  (3-ethyl  pentene-2). 

C2H5  C2H5 


C2H3  —  C  —  OH-     --*C2H5C 

C2H5  CH. 


CH, 


and  5-iodo  heptane,  C3H7  —  CHI  —  C3H7,  by  virtue  of  its  symmetry, 
yields  pure  y-heptene  when  decomposed  by  caustic  alkali. 

The  simpler  primary  alkyl  chlorides  and  bromides  on  treatment 
with  caustic  alkali  in  methyl  or  ethyl  alcohol  yield  chiefly  methyl  or 
ethyl  ethers  but  alkyl  iodides  of  five  or  more  carbon  atoms,  particu- 
larly secondary  and  tertiary  derivatives,  yield  olefines  almost  quanti- 
tatively.146 

Organic  bases,  aniline,  quinoline  and  the  like  have  frequently  been 
employed  to  remove  halogens  with  success.  Tertiary  halides,  like  ter- 
tiary alcohols,  are  easily  decomposed  and  Klages  147  has  employed  pyri- 
dine  for  tertiary  chlorides.  Decomposition  of  alkyl  halides  by  heat  is 
usually  attended  by  rearrangements  and  often  with  rupture  of  the  car- 
bon structure,  and,  in  some  cases,  by  condensation  or  polymerization, 
but  many  substances  catalyze  this  decomposition  of  the  halides,  so 
that  lower  temperatures  may  be  employed  and  subsequent  changes  of 
the  olefines  may  be  minimized.  Nearly  quantitative  yields  of  ethylene 

145  Auster well  later  synthesized  isoprenes  in  a  similar  way,  treating  vinyl-magne- 
sium bromide  with  beta-chloropropylene, 

/  CH  =  CH2  /  Cl  /  CH  =  CH2 

'*'    !  "1  Mg  +CH3C  »MgBrCl  +  CH3C 

\  Br  \CH2  \  CH2 

J.  Chem.  Soc.  Abs,  102,  525    (1912). 

149  Nef,  Ann.  S09,  126   (1899)  ;  318,  1   (1901). 
™  Ber.  35,  2633    (1902). 


THE  ETHYLENE  BOND  153 

may  be  obtained  from  ethyl  chloride  by  heating  in  contact  with  barium 
chloride  and  chloropentanes  can  be  decomposed  to  amylenes  in  this 
manner.148  A  large  number  of  processes  for  the  decomposition  of  bornyl 
chloride  to  camphene  have  been  described  in  connection  with  the  syn- 
thesis of  camphor.  Bornyl  chloride  is  remarkably  stable  and  most  of 
the  successful  reactions  are  carried  out  within  the  range  160°  to  190°. 
Usually  an  alkaline  substance  or  mixture  is  sought  which  will  dissolve 
the  bornyl  chloride  forming  a  homogenous  reaction  mixture  and  pat- 
ented methods  refer  to  the  use  of  sodium  phenolate,  sodium  soaps  such 
as  oleate,  linoleate,  etc.,  sodium  acetate  in  acetic  acid,  aniline,  quino- 
line,  etc.  Zinc  chloride  catalyzes  the  decomposition  of  bornyl  chloride 
but  rapidly  polymerizes  the  camphene  formed. 

Certain  defines  are  often  most  readily  made  by  the  decomposition 
of  halogenated,  hydroxy  or  unsaturated  fatty  acids  but  these  methods 
are  by  no  means  generally  applicable.    Pure  p-butylene  is  easily  made 
from  bromotiglic  acid  by  heating  with  soda  in  aqueous  solution.149 
CH3 

CH3CHBrCH         >  CH3CH  =  CHCH3  +  C02  +  NaBr 

C02Na 

The  p-halogen  derivatives  of  the  fatty  acids  are  decomposed  very 
easily  by  alkalies  and  the  resulting  unsaturated  acids  frequently  lose 
C02  on  heating  or  distilling  to  give  an  olefine.  p-bromoisobutyric  acid 
is  quantitatively  decomposed  by  aqueous  barium  hydroxide  to  methyl 

CH3 

acrylic  acid,  'CH .  CO2H >  C .  CO,H  and  a-bromo- 

CH/7          " 

butyric  acid,  considerably  more  stable,  also  yields  methyl  acrylic  acid 
by  treating  with  25%  caustic  soda.150  Normal  p-bromo  fatty  acids  on 
heating  with  water,  dilute  alkali,  or  by  destructive  distillation,  yield 
more  of  the  a-(3-unsaturated  acid  than  the  p-y-unsaturated  acid. 
Wallach  151  has  made  use  of  the  instability  of  the  p-hydroxy  acids  to 

"8  Badische,  German  Pat.  255,519,  J.  Chem.  Soc.  104,  438  (1913);  German  Pat. 
268,100,  Chem.  Zentr.  1914,  I,  308;  Sabatier  &  Mailhe,  J.  Chem.  Soc.  104,  330  (1913)  ; 
Braun  and  Deutsch,  Ber.  45,  1271  (1912). 

According  to  Mathews,  Bliss  and  Elder,  the  decomposition  of  alkyl  halides  within 
tne  range  100°-700°  is  catalyzed  by  water,  either  in  the  presence  or  absence  of  other 
catalysts.     Brit.  Pat.  16,828    (1912)  ;  17,234   (1912). 
6  Pagenstecher,  Ann.  195,  112   (1879). 

"Engehorn,  Ann.  200,  68   (1880)  ;  Bischoff,  Ber.  £4,  1041   (1891). 

lslAnn.  S65,  257   (1909). 


154      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

synthesize  defines  containing  the  methene  group.  Using  the  method  of 
Reformatsky  of  condensing  ketones  or  aldehydes  with  bromoacetic 
ester  by  means  of  zinc,  Wallach  proceeded  as  indicated  by  the  follow- 
ing reactions,  the  hydroxy  acids  being  dehydrated  by  heating  with 
acetic  anhydride. 


and  from  nopinone  (3-pinene  was  synthesized, 


\ 


C=CHC02H 


C=cii 


Tertiary  alcohols  decompose  so  readily  that  they  are  difficult  to 
acetylate.  Glacial  acetic  acid  at  150°  to  155°,  or  acetic  anhydride  con- 
taining a  little  zinc  chloride,  or  sulfuric  acid,  yields  chiefly  unsaturated 
hydrocarbon.  Thus  trimethyl  carbinol  yields  isobutylene,152  diethyl- 
propylcarbinol  yields  an  octene,153  etc. 

Primary  and  secondary  alcohols  of  high  molecular  weight  may  be 
converted  to  olefines  by  the  method  of  Krafft,15*  i.  e.,  treating  with 
palmityl  chloride  and  distilling  the  palmitic  ester  slowly  at  ordinary 
pressure.  In  the  terpene  series  the  method  developed  by  Tschugaeff  155 
consisting  in  heating  the  methylxanthogenate  ester  of  the  alcohol,  has 
given  excellent  results.  Very  little  heat  is  usually  required  and  the 
probability  of  rearrangement  or  decomposition  is  greatly  lessened;  in 
fact,  the  methylxanthogenate  esters  of  tertiary  alcohols,  if  formed,  de- 
compose spontaneously  at  ordinary  temperatures.  Henderson  156  pre- 

162  Menschutkin,  Ann.  197,  204   (1879). 

163  Mason,    Compt.   rend.   132,   483    (1901);    Henry,    Compt.   rend.   1U,   552    (1907); 
147,  1260    (1908). 

154  Ber.  16,  3020  (1883). 
166  Ber.  32,  3332  (1899). 
166  J.  Chem.  Soc.  91,  1620  (1910)  ;  99,  1903  (1911). 


THE  ETHYLENE  BOND  155 

pared  very  pure  bornylene  from  the  methylxanthogenate  ester  of  bor- 
neol. 

Heating  primary  or  secondary  alcohols  with  mineral  acids  rarely 
gives  good  results  except  with  the  simpler  members,  as  in  the  well- 
known  methods  of  preparing  ethylene  and  propylene,  using  sulfuric  or 
phosphoric  acids.  Wallach  showed  that  concentrated  formic  acid  15T 
or  oxalic  acid 158  give  better  results  in  the  terpene  series  than  mineral 
acids.  Potassium  acid  sulfate  has  been  employed  with  good  results,  as 
in  the  conversion  of  borneol,  which  is  relatively  quite  stable,  to  cam- 
phene.159  When  potassium  acid  sulfate  or  phosphorus  pentoxide  is  used 
to  dehydrate  cyclohexanol-1-acetic  acid,  cited  above,  the  resulting 
product  is  A1- 2  cyclohexene  acetic  acid  instead  of  the  A1(7)  acid  which  is 
obtained  with  acetic  anhydride. 

Sabatier  and  Mailhe  16°  have  shown  that  phosphorus,  carbon,  anhy- 
drous calcium  sulfate,  basic  aluminum  sulfate  and  many  metallic  oxides 
promote  the  dehydration  of  alcohols.  The  corresponding  olefine  hydro- 
carbon is  usually  produced,  although  alumina  at  210°  causes  some  ether 
to  be  formed.  Ipatiev  found  that  under  higher  pressures  the  formation 
of  ether  was  considerably  increased.  Baskerville  was  unable  to  detect 
ether  in  ethylene  resulting  from  the  decomposition  of  alcohol  in  con- 
tact with  thoria  at  temperatures  as  low  as  250°. 161  Sabatier  and 
Mailhe  studied  a  series  of  catalysts  and,  within  the  temperature 
range  300°-350°,  ethyl  alcohol  gave  varying  yields  of  ethylene  and 
hydrogen,  the  latter  being  formed  together  with  acetaldehyde, 

CH3CH2OH >CH3CHO  +  H2.    Thoria,  alumina  and  blue  oxide 

of  tungsten  at  340°-350°  gave  practically  quantitative  yields  of  ethyl- 
ene and  the  other  catalysts  gave  the  results  indicated  in  the  following 
table: 

Per  cent  ethylene 

Th02   : 100. 

A12O3    98.5 

W203   98.5 


Dehydration  and 
dehydrogenation 


Cr20,  

91.  ^ 

SiO2  . 

84 

TiO2   

63 

BeO   

45 

ZrO2   

45 

U308    

24. 

23. 

FeoO3  . 

14. 

V2O3    . 

9 

ZnO  . 

5.  J 

™  Ann.  291,  361   (1896)  ;  S56,  243  (1907). 

168  Ann.  275,  106   (1893). 

169  Wallach,  Ann.  230,  239  (1885). 

190  Ann.  Ohim.  Phys.  VIII.  20,  289  (1910). 
191 J.  Am.  Chem.  Soc.  S5,  93   (1913). 


156      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

SnO 0.  ^ 

CdO    0. 

MgO  0.    f        Dehydrogenation 

Cu    ..! 0. 

Ni 0.  J 

Engelder 162  showed  that  in  the  presence  of  A1203,  Si02,  Zr02  and 
Ti02  the  equilibrium,  alcohol  ?±  water  +  ethylene,  could  be  displaced 
by  the  addition  of  water  vapor  to  the  incoming  alcohol.  Kaolin  within 
the  range  350°-400°  is  particularly  efficient  in  producing  ethylene.163 
Ipatiev,  prior  to  the  work  of  Sabatier  and  Mailhe  quoted  above,  had 
shown  the  wide  applicability  of  alumina  as  a  dehydrating  catalyst.164 
He  prepared  isobutylene  and  pure  propylene  using  alumina  as  a  cat- 
alyst and  butylene  has  been  made  from  n. butyl  alcohol,  on  an  indus- 
trial scale,  by  the  same  method.165  Senderens  found  that  amorphous 
silica  is  much  more  active  than  ground  quartz  and  aluminum  phos- 
phate is  also  an  excellent  catalyst;  Senderens  obtained  noteworthy  re- 
sults by  decomposing  cyclohexanol  at  300°,  to  cyclohexene  and  men- 
thol to  menthene.166  Pinacone  gives  excellent  yields  of  dimethylbuta- 
diene  when  passed  over  alumina  at  450°,  but  the  best  yields  are  ob- 
tained in  vacuo.™ 

The  decomposition  of  tertiary  amines  has  been  employed  as  a 
laboratory  method  but  the  preparation  of  these  amines  is  compara- 
tively costly  and  difficult  though  several  processes  for  the  preparation 
of  dienes,  leading  to  the  synthesis  of  rubber,  which  involve  this  ter- 
tiary amine  method,  have  been  patented.168  As  pointed  out  above,  the 
decomposition  of  the  tertiary  amines  usually  takes  place  at  compara- 
tively low  temperatures,  thus  lessening  the  probability  of  decompo- 
sition or  rearrangement  of  the  resulting  olefine.  Willstatter  and 
Schmaedel,169  made  cyclobutene  in  this  way. 

CH2  —  CH  —  NH2 »  CH2  —  CH  —  N  (CH3)  3          CH2  —  CH 

CH2  — CH2  CH2  — CH2     OH  CH2  — CH 

+  N(CH3)3  +  H20 

The  Grignard  reaction  has  sometimes  been  applied  to  the  synthesis 
of  olefines  in  ways  other  than  noted  above.  In  rare  instances  the  Grig- 

182  J.  Phys.  Chem.  21,  676   (1917). 

163  The  activity  of  these  catalysts  is  gradually  diminished  as  they  become  impreg- 
nated with  carbon,  evidently  formed  by  the  decomposition  of  ethylene  to  methane  and 
carbon. 

^Ber.  36,  1997   (1903)  ;  3J,,  596,  3579   (1901). 

MS  Newman,  Can.  Chem.  J.  1920,  47;  King,  J.  Chem.  Soc.  115,  1404   (1919). 

166  Compt.  rend.  11^,  1109  (1907)  ;  1J,6,  125  (1908)  ;  Bayer  &  Co.  Brit.  Pat.  4,076 
(1913). 

167Badische,  French  Pat.  417,275   (1910). 

168  J.  Chem.  Soc.  102,  I,  821   (1912). 

169  Ber.  38,  1992   (1905). 


THE  ETHYLENE  BOND 


157 


nard  complex  RC< 


OMgX 

R, 


breaks  down  spontaneously,  but  heat  is 


usually  required  to  effect  decomposition  to  the  olefine.170 

The  decomposition  of  hydrocarbons  by  heat  ha&  not  been  employed 
for  the  preparation  of  pure  olefines,  but  it  is  well  known  that  the  pyro- 
lytic  products  of  paraffine,  petroleum  oils  and  the  like  are  rich  in 
olefines.  Pressure,  as  in  distillation  of  heavy  oils  under  pressure,  di- 
minishes the  proportion  of  olefines  in  the  product  and  decomposition  by 
heat  under  vacuum  increases  the  proportion  of  olefines.  Dilution  of  the 
original  hydrocarbon  vapors  with  an  inert  gas  or  steam  also  has  this 
effect.171 

The  reduction  of  the  ketone  group  to  the  CH2  group,  in  the  pres- 
ence of  a  cyclopropane  ring  or  unsaturated  bonds  of  the  ethylene  type 
and  without  reducing  these  double  bonds,  may,  in  certain  instances,  be 
accomplished  by  forming  the  hydrazine  derivative  of  the  ketone  and 
then  decomposing  this  by  solid  caustic  potash.  Thus  carone  gives 
carane,  without  rupture  of  the  cyclopropane  ring,  and  ionone  yields  the 
corresponding  unsaturated  hydrocarbon.172 


CH. 


CH=CH 

C=N.NH2 

CH3 


CH: 


"o  Harries  &  Weil,  Ann.  348,  363  (1905)  ;  Klages,  Ber.  S9,  2306   (1906)  ;  Barbier  & 
Locquin,  Chem.  Zentr.  1913,  II,  28. 

171  Greenstreet,  U.  S.  Pat.  1,110,925. 

"'Kishner,  J.  Russ.  Phys.-Chem.  Soc.  43,  1398,  1563   (1911). 


Chapter  V.     Acyclic  Unsaturated 
Hydrocarbons. 

Remarkably  few  hydrocarbons  of  this  series  are  known.  Many 
which  have  been  described  are  undoubtedly  mixtures  and  the  constitu- 
tions assigned  to  many  of  them  are  undoubtedly  incorrect.  This  is 
particularly  true  of  olefines  of  the  type  RCH2CH  =  CH2.  The  simpler 
olefines  are  very  reactive  and  the  most  promising  outlook  for  the 
chemical  utilization  of  petroleum  is  undoubtedly  in  the  direction  of 
these  simpler  olefines,  including  the  gaseous  olefines,  ethylene  and 
propylene,  and  the  low  boiling  highly  reactive  olefines  such  as  the 
butylenes,  amylenes  and  hexylenes. 

Ethylene 

One  liter  of  ethylene  under  standard  conditions  weighs  1.2519 
grams.1  Its  boiling  point  at  760  mm.  according  to  Cailletet 2  is  — 105° 
and  according  to  Ladenburg  and  Kriigel 3  is  — 105.4° ;  Burrell  and 
Robertson  4  give  — 103.9°  as  the  boiling-point.  Its  melting-point  is 
—  169°.  Its  critical  temperature  is  9.5°  ±  0.1,  critical  pressure  50.65 
±  0.1  atmospheres.5  Its  heat  of  combustion  is  stated  to  be  333,350 
and  341,400  calories  (Thomsen6)  and  345,800  calories  (Mixter7). 
Data  on  the  compressibility  of  ethylene  and  the  extent  of  its  deviation 
from  the  behavior  of  a  perfect  gas  under  pressure  at  ordinary  atmos- 
pheric temperature  have  recently  been  published,  compressed  ethylene, 
in  steel  cylinders,  for  welding  and  cutting  now  being  commercially 
available.8 

Water  at  0°  dissolves  approximately  0.25%  ethylene.  The  gas  is 
markedly  soluble  in  ammoniacal  cuprous  chloride,  but  not  in  am- 

1Ct.  Malisoff  &  Egloff,  J.  PTiys.  Ghem.  23,  65   (1919). 

'Compt.  rend.  94,  1224  (1882). 

•Ber.  32,  1818   (1899). 

*J.  Am.  Chem.  Soc.  37.  1893  (1915). 

*J.  Chim.  Phya.  10,  504   (1913). 

•  Thermochem,   Unters,  4,   64. 

7  Am.  J.  Sci.   (4),  4,  51   (1897). 

•According  to  British  Patents  146,332  and  147,051  (1920),  ethylene  may  be 
separated  from  coal  gas  or  oil  gas  by  passing  the  gas  through  a  series  of  absorbent 
materials  at  low  temperatures. 

158 


c: 
E 


3  S-Q 


300 


<3 

-er 

ID 

<u 

E 

i — . 
<u 


2,00 


100 


o 
-5 


I6.3°C 
30.|'C 

SO*C 


•TOO       1000       iroo      zooo      troo      3ooo      35-00      torn 

Pressure,  PouncU  per  so.. inch 

Compressibility  of  Ethylene. 


159 


160      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

moniacal  silver  chloride.  Ethylene  is  also  markedly  soluble  in  pe- 
troleum oils  under  moderate  pressures;  oil  gas  scrubbed  with  pe- 
troleum oils  under  pressures  of  50  to  150  pounds  loses  by  solution  in 
the  oil  much  more  ethylene  and  propylene  than  corresponds  to  the 
partial  pressure  of  these  defines  in  the  gas  mixture.  On  removing 
the  pressure  on  the  oil  solution,  gas  is  liberated  which  is  much  richer 
in  defines  than  the  original. 

Ethylene  is  most  easily  made  by  passing  ethyl  alcohol  over  kaolin 
at  350°  to  400°.  Ethylene  was  made  by  this  method  on  a  large  scale 
during  the  late  war.9  When  ethyl  alcohol  is  passed  over  metals  at 
elevated  temperatures  various  amounts  of  acetaldehyde  are  formed. 
Zinc  dust  at  550°  gives  a  50%  yield  of  ethylene.  Ipatiev  10  used  fire 
clay  and  alumina  with  excellent  results  and  Engelder11  states  that 
with  alumina  at  350°  the  resulting  gas  contains  98.5%  ethylene. 
Sprent12  gives  a  slightly  higher  figure  as  the  best  working  tempera- 
ture when  using  alumina,  i.  e.,  360°.  This  method  of  preparing  ethyl- 
ene is  intimately  connected  with  the  stability  of  ethylene  to  heat  and 
the  presence  of  various  contact  substances.  As  pointed  out  by  Bone 
and  Coward 13  the  importance  of  the  time  factor  on  the  character  and 
proportions  of  the  products  resulting  from  the  passage  of  substances 
through  hot  tubes  has  frequently  been  overlooked.  Ethylene  is  very 
rapidly  decomposed  in  contact  with  nickel  at  300°,  carbon,  ethane, 
methane  and  hydrogen  being  formed.  This  decomposition  is  much 
slower,  in  contact  with  iron,  but  is  quite  rapid  above  350°,  but  ac- 
cording to  Ipatiev  polymerization  occurs  in  the  presence  of  iron  or  cop- 
per at  400°-450°.  In  the  absence  of  catalysts  such  as  nickel,  no  hy- 
drogen is  formed  from  ethane  at  450°.  According  to  Day  14  ethylene 
appears  to  be  very  slowly  condensed  at  350°  to  400°,  the  residual  gas 
containing  methane  and  ethane.  According  to  the  early  researches  of 
Berthelot,  ethylene  condenses  with  benzene  to  form  anthracene  when 
the  two  hydrocarbons  are  passed  together  through  a  red-hot  tube. 
This  reaction  has  recently  been  examined  by  Zanetti  and  Kandell,15 
who  find  that  the  maximum  yields  of  anthracene  are  obtained  at  900° 
to  925°  C. 

Numerous  attempts  have  been  made  to  prepare  ethylene  by  partial 

•Norris,  J.  Ind.  &  Ena.  Chem.  11,  817   (1919). 
™Ber.   85,   1047    (1902);   86,   1990    (1903). 

11  J.  Phys.  Chem.  21,  676    (1917). 

12  J.  Soc.  Chem.  Ind.  S2,  171   (1913). 

18  Rep.  Brit.  Assoc.  1915,  368;  Soc.  93,  1197   (1908). 

"Am.  Chem.  J.  8,  153   (1886). 

"  J.  Ind.  &  Eng.  Chem.  13,  208  (1921). 


ACYCLIC  UNSATURATED  HYDROCARBONS  161 

hydrogenation  of  acetylene,  but  so  far,  without  commercial  success. 
Karo 16  and  others  17  state  that  90  to  95%  conversion  to  ethylene  can 
be  effected  in  the  presence  of  active  nickel  at  about  100°.  Ethylene, 
itself,  is  very  rapidly  hydrogcnated  to  ethane  in  the  presence  of  nickel 
at  150°.  The  activity  of  nickel  is  quickly  impaired  by  the  separation 
of  carbon  and  copper  is  not  very  effective,  but  the  change  is  rapid  in 
the  presence  of  platinum  black  at  185°,  and  aqueous  colloidal  plati- 
num or  palladinum  effect  rapid  reaction  at  room  temperature.18  In 
this,  as  in  many  similar  reactions  in  which  gas  and  liquid  phases  are 
concerned,  the  rate  of  solution  of  the  gas  is  the  chief  time  controlling 
factor.  During  the  war  this  problem  was  investigated  in  the  labora- 
tory at  Edgewood- Arsenal,  on  account  of  the  importance  of  ethylene 
in  the  manufacture  of  "mustard  gas."  The  process  was  evidently  not 
carried  out  on  an  industrial  scale  but  it  was  ascertained  that  in  the 
presence  of  catalytic  nickel  prepared  by  reduction  at  300°,  both  ace- 
tylene and  ethylene  are  hydrogenated  at  temperatures  as  low  as  —  10°. 
No  deposition  of  carbon  on  the  catalyst  was  noticed  when  the  reaction 
was  carried  out  at  room  temperatures.  Gas  mixtures  containing  ap- 
proximately 80%  ethylene  were  obtained,  the  remaining  gas  consist- 
ing of  ethane,  nitrogen  and  a  little  acetylene. 

Ethylene  is  a  minor  product  in  the  electrolysis  of  salts  such  as  ace- 
tates, malonates  and  succinates:  it  can  be  made  from  ethylene  bromide 
by  Gladstone's  copper-zinc  couple,  and  certain  metallic  carbides  react 
with  water  to  give  small  proportions  of  ethylene  (barium  carbide  and 
silicide  mixture  yields  a  gas  containing  15%  ethylene).  But  the  only 
method,  other  than  the  hot  kaolin  method,  which  is  of  preparative 
value,  is  the  old  familiar  laboratory  method  of  passing  alcohol  vapor 
into  hot  sulfuric  or  phosphoric  acid.  In  this  method  of  preparation  a 
small  proportion  of  hydrocarbon  oil  is  always  noticed  in  the  wash  bot- 
tles, and  this  oil  is  probably  a  condensation  product  or  polymer  of 
ethylene.19  Thus  zinc  chloride  at  275°  converts  ethylene  into  an  oily 
polymer  of  specific  gravity  (15°)  0.751  and  anhydrous  aluminum  chlo- 
ride effects  a  similar  change  at  room  temperature. 

Ethylene  may  be  oxidized  without  great  difficulty  to  formaldehyde, 

"Karo,  Ger.  Pat.  253,100  (1911)  ;  Sabatier  &  Sendereias,  Compt.  rend.  128,  1173 
(1899)  ;  130,  1559,  1628  (1900)  :  131,  40,  187  (1900)  ;  Paal,  Ber.  48,  275  (1915)  ;  Paal  & 
Schwarz,  Ber.  51,  640  (1918),  claim  that  colloidal  palladium  gives  the  best  results.  A 
particularly  important  paper  has  just  appeared  by  Ross,  Culbertson  and  Parsons,  J. 
Ind.  d  Eng.  Chem.  13,  775  (1921). 

"Lane,   Ryberg  &   Kinberg,   Ger.   Pat.   262,541    (1913). 

18  Sabatier  &  Senderens.  Compt.  rend.  131,  40  (1900)  ;  Paal  &  Hartman,  Ber.  42, 
2239  (1909)  ;  .',8,  994  (1915). 

18  Montmollin  [Bull.  Soc.  chim.  (4),  19,  242  (1916)]  has  examined  this  oil  mixture 
and  states  that  it  consists  chiefly  of  alkylated  naphthenes. 


162      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

oxalic  and  acetic  acids,  glycol,  formic  acid,  etc.,  but  these  oxidation 
products  are  themselves  oxidized  more  rapidly  than  ethylene.  The 
major  products  of  the  oxidation  of  ethylene  are,  therefore,  usually  C02 
and  water  and  large  yields  of  intermediate  products  are  not  to  be  ex- 
pected. 

At  400°  with  insufficient  oxygen  for  complete  combustion,  a  little 
formaldehyde  is  formed.20  With  equal  volumes  of  oxygen,  carbon 
monoxide  and  hydrogen  are  produced;  with  less  than  an  equal  volume 
of  oxygen  Lean  and  Bone  21  believed  two  reactions  to  be  involved, 


C2H4 

2C2H4 

Bone  and  Wheeler  22  studied  the  oxidation  of  ethylene  by  oxygen 
at  temperatures  within  the  range  250°  to  400°,  but  according  to  a  re- 
cent paper  by  Willstatter  23  the  oxidation  to  formaldehyde  is  not  rapid 
below  500°.  As  shown  by  F.  G.  Phillips,  combustion  of  ethylene  takes 
place  at  lower  temperatures  in  the  presence  of  osmium  than  with  other 
catalytic  surfaces  and  Willstatter  finds  that  in  the  presence  of  this 
metal  oxidation  of  ethylene  begins  at  130°,  carbon  dioxide  and  water 
being  practically  the  only  products.  In  the  presence  of  copper  or  silver 
practically  no  formaldehyde  is  produced,  and  in  the  case  of  copper  oxi- 
dation is  fairly  rapid  at  250°.  Willstatter  made  use  of  the  observation 
that  when  ethylene  is  diluted  with  an  inert  gas  the  thermal  decompo- 
sition of  the  ethylene  itself  is  greatly  reduced.  Metallic  surfaces  cat- 
alyse the  thermal  decomposition  of  ethylene  and  Willstatter  accord- 
ingly obtained  the  best  yields  of  formaldehyde  by  operating  without  a 
catalyst  at  about  585°,  using  a  gas  mixture  containing  19.38  per  cent 
ethylene  and  7.58  per  cent  oxygen.  Under  these  conditions  he  ob- 
tained approximately  50  per  cent  of  the  theory  of  formaldehyde. 

Ozone  reacts  vigorously  with  ethylene,24  an  explosive  compound 
being  formed.  In  the  presence  of  water  formaldehyde,  formic  acid, 
carbon  monoxide  and  hydrogen  peroxide  are  among  the  reaction  prod- 
ucts. 

Ethylene  and  oxygen  in  sunlight  at  ordinary  temperatures  do  not 
react  but  under  the  influence  of  ultraviolet  light,  oxidation  to  C02,  CO 

«>Nef,  Ann.  298,  202   (1899). 

21  J.   Ghent.   Soc.   115,  144    (1892). 

22  J.  Gliem.  Soc.  83,  1074   (1903). 
*'Ann.  422,  36  (1921). 
"Harries,  Ann.  &$,  288   (1910). 


ACYCLIC  UNSATURATED  HYDROCARBONS  163 

and  formic  acid  results.25  According  to  Taylor 26  ethylene  and  oxygen 
react  at  ordinary  temperatures  in  the  presence  of  activated  charcoal. 
Chromic  acid  oxidizes  ethylene,  with  difficulty  to  C02,  formic  and 
acetic  acids.27  Potassium  permanganate  in  dilute  sulfuric  acid  yields 
C02,  formic  and  acetic  acids,  but  neutral  or  alkaline  permanganate 
yields  glycol  and  oxalic  acid.28 

Ethylene  combines  directly  with  a  large  number  of  substances  and 
while  many  of  these  reactions  have  been  known  for  a  great  many 
years,  a  few  of  them  have  become  industrially  important  only  within 
very  recent  years.  Ethylene  chlorohydrin  was  made  by  Carius  29  and 
others  by  treating  ethylene  with  dilute  aqueous  hypochlorous  acid. 
Gomberg 30  has  recently  shown  that  the  reaction  of  ethylene  and  hypo- 
chlorous  acid  takes  place  so  rapidly  that  practically  quantitative  yields 
of  the  chlorohydrin  are  obtained  by  agitating  ethylene  with  cold  chlor- 
ine water,  although  free  chlorine  is  also  present.  Methods  suit- 
able for  large  scale  manufacture  of  ethylene  and  propylene  chlo- 
rohydrins,  using  chlorine  and  cold  aqueous  solutions  of  sodium  car- 
bonate or  bicarbonate,  have  recently  been  described.31  Ethylene  bro- 
mohydrin  has  recently  been  made  by  passing  ethylene  and  bromine 
vapor  separately  into  ice  water,  keeping  the  concentration  of  the  bro- 
mine in  the  solution  very  low.32  The  bromohydrin  had  previously  been 
made  by  the  action  of  HBron  ethylene  glycol  or  by  the  action  of  PBr3 
on  the  glycol.  The  bromohydrin  boils  with  slight  decomposition,  at 
146°-150°  and  has  a  density,  20°,  of  1.7629. 

Ethylene  chlorohydrin  reacts  with  sodium  azide,  the  chlorine  being 
replaced  by  the  triazo  group.33  (Vinyl  bromide  does  not  react  with 
sodium  azide.)  By  converting  the  triazoethyl  alcohol  to  the  bromide 
and  replacing  the  bromine  with  iodine,  the  resulting  triazoiodine  deri- 
vative can  be  decomposed  by  alkali,  removing  HI  and  yielding  triazo- 
ethylene.  The  boiling-point  of  triazoethylene  is  26°,  or  10°  higher  than 
the  corresponding  bromide  CH2  =  CHBr. 

CH,C1  CH,N3  CH2N3  CHN3 

|  +NaN3 »J  >|  >|| 

CHOH  CH2OH  CHJ  CH2 

"Berthelot  and  Gaudechon,  Compt.  rend.  150,  1327   (1910). 
29  Trans.  Am.  Electrochem.  Soc.  1919,  167. 

27  Chapman   &  Thorpe,   Ann.   V&,  182    (1867)  ;   Othmar  &   Feidler,   Ann.    197,    243 
(1879). 

28  Ann.  150,  373  (1869)  ;  Ber.  21,  1234   (1888).     Cf.  Evans  on  oxidation  of  ethylene 
glycol  by  permanganate,  J.  Am.  Chem.  Soc.  41,  1385   (1919). 

"Ann.  126,  197   (1863)  ;  Butlerow,  Ann.  144,  40   (1867). 

so  J.  Am.  Chem.  Soc.  41,  1414  (1919). 

31  Brooks,  Chem.  d  Met.  Eng.  22,  629  (1920). 

82  Read  &  Hook,  J.  Chem.  Soc.  in,  1214   (1920). 

"Forster  &  Newman,  J.  Chem.  Soc.  97,  2570    (1910). 


164      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

Ethylene  chlorohydrin  gave  promise  of  becoming  of  some  impor- 
tance during  the  recent  war,  as  an  intermediate  in  the  manufacture 
of  dichloroethyl  sulfide  (mustard  gas),  but  another  reaction  of  ethylene, 
i.  e.,  its  reaction  with  sulfur  chloride,  first  discovered  by  Guthrie,34 
proved  to  be  more  suited  to  large  scale  production  and  was  adopted  in 
all  the  Allied  countries.  The  experimental  conditions,  of  which  Guth- 
rie's  work  gave  little  more  than  a  hint,  were  worked  out  by  Pope  35  and 
the  large  scale  operations  worked  out  by  Levinstein.  Gibson  and 
Pope  36  showed  that  when  the  reaction  between  ethylene  and  sulfur 
chloride  is  carried  out  above  70°  considerable  decomposition  occurs 
and  Pope  and  his  assistants  showed  in  a  later  paper  3T  that  practically 
quantitative  yields  are  obtained  when  the  ethylene  contains  a  little 
alcohol  vapor  but  when  pure  ethylene  is  employed  the  product  is  not  so 
pure,  thus  explaining  the  discrepancies  reported  by  other  workers.  The 
sulfur  liberated  in  the  reaction  appears  to  be  retained  largely  in  a 
colloidal  condition  and  may  be  separated  by  dissolving  the  dichloro 
sulfide  in  kerosene  and  then  separating  the  mustard  gas  from  the 
kerosene  solution  by  chilling.  Distillation  in  vacuo  readily  yields  pure 
(3(3- dichloroethyl  sulfide.  In  Germany  the  chlorohydrin  method  of 
making  mustard  gas  was  employed. 

Ethylene  reacts  with  selenium  monochloride  38  to  give  free  selenium 
and  the  product  Cl2Se(CH2CH2Cl)2. 

The  reactions  of  the  two  manufacturing  processes  for  mustard  gas 
are  as  follows: 

(1)       CH2 

||        +HOC1 
CH 


2CH2OH 

+Na2S 
H2C1 


| 
C 


CH2C1 


(2) 

2 

34  Ann.  119,  91    (1861)  ;  121,  108   (1862). 

36  J.  Soc.  Chem.  Ind.  38,  344R,  434R  (1919)  ;  Green,  J.  Soc.  Chem.  Ind.  38,  363R, 
469R  (1919). 

MJ.   Chem.  Soc.  117,  271    (1920). 

87  J.  Chem.  Soc.  119,  634   (1921). 

88Bausor,  Gibson  &  Pope,  J.  Chem.  Soc.  117,  1453  (1920)  :  Heath  &  Semon  J  Ind 
d  Eng.  Chem.  12,  1100  (1920). 


ACYCLIC  UNSATURATED  HYDROCARBONS  165 

CH2C1  CH.C1 

+  S 
CH2 S CH2 

Phosgene  reacts  with  ethylene  under  the  influence  of  light  as  fol- 
lows.39 


CH2  CH,C1 

_j_COC!2 >  I 

!H,COC1 


v^  j-j>2  v>i 

-f  COC12 >  I  (Chloropropiony  1  chloride) . 

CH0  CI 


Norris  and  Couch  40  have  shown  that  benzoyl  chloride  reacts  with 
ethylene  in  the  presence  of  anhydrous  aluminum  chloride  to  give  phenyl 
vinyl  ketone,  a  reaction  probably  capable  of  considerably  wider  appli- 
cation. Ethylene  is  readily  absorbed  by  anhydrous  aluminum  chloride 
and  benzene  to  form  mono-  and  poly-substituted  ethyl  benzenes.41 

Chlorine  and  bromine  42  react  smoothly  with  ethylene  to  give  the 
symmetrical  dihalides.  The  addition  of  chlorine  to  ethylene  to  form 
ethylene  chloride  or  "Dutch  liquid"  was  first  carried  out  in  1796  and 
Faraday  later  treated  oil  gas 43  with  chlorine  obtaining  ethylene  chlo- 
ride together  with  other  chlorinated  products.  Although  this  reaction 
has  been  known  since  this  early  date,  no  very  thorough  study  of  it  has 
been  made.  Dry  chlorine  and  ethylene  react  exceedingly  slowly.  Ethyl- 
ene passed  into  chlorine  water  yields  ethylene  chlorohydrin  almost 
exclusively;  cold  dilute  bromine  water  yields  both  ethylene  bromide 
and  ethylene  bromohydrin.  In  chlorinating  ethylene,  it  is  difficult  to 
limit  the  chlorination  to  the  dichloride,  trichloroethane  and  still  more 
highly  chlorinated  products  being  formed.  The  introduction  of  ethyl- 
ene into  liquid  chlorine  in  the  cold,  under  pressure,  gives  excellent 
yields  of  ethylene  chloride,44  and  chlorination  in  the  presence  of  char- 
coal, alumina  or  other  very  porous  material  is  stated  to  give  good 
yields.45  Another  patentee  employs  solid  calcium  chloride  as  a  cat- 
alyst.46 Higher  defines,  amylenes  and  hexylenes,  yield  dichlorides  when 
treated  with  sulfuryl  chloride  below  30°. 47  When  chlorine  is  absorbed 
in  cold  bromine  in  the  proportions  required  by  the  hypothetical  sub- 

"Lippman,  Ann.  129,  81    (1864). 

40  J.  Am.  Chem.  Soc.  J&,  2330    (1920). 

41Balsohn,  Bull.  Soc.  chim.    (2),  31,  529    (1879). 

42  According  to  Plotnikov,   Chem.  Abs.  1917,  48.  ethylene  and  bromine  react  even 
at  —  80°  in  the  dark. 

43  The  oil  gas  used  by  Faraday  was  probably  made  from  fatty  oils,  which,  however, 
closely  resembles  oil  gas  made  from  mineral  oils  in  its  general  character. 

44  Curme,   U.   S.   Pat.   1,315,545  ;   1,315,547. 

45  Harding,    Brit.   Pat.    126,511    (1918). 

46  Sniythe,    Gas.    J.   149,   691    (1920).     A   yield   of   50%    ethylene   chloride   by    this 
method  is  reported. 

4r  Badische  Co.,  J.  Soc.  Chem.  Ind.  1912,  151. 


166      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

stance  BrCl  and  ethylene  is  then  introduced,  the  principal  product  is 
CH2Cl.CH2Br,  which  appears  to  be  the  only  real  evidence  of  the  ex- 
istence of  the  compound  Cl.Br.48  Bromine  has  practically  no  action 
on  ethylene  bromide.  Iodine  reacts  slowly  with  ethylene  in  direct 
sunlight  or  on  heating  to  60°. 49 

Iodine  monochloride  and  ethylene  yields  ethylene  chloride  and  free 
iodine.  Concentrated  hydriodic  and  hydrobromic  acids  combine  slowly 
with  ethylene  at  100°. 

Boron  trifluoride  reacts  with  ethylene  forming  the  product  C2H3BF2 
boiling  at  125°. 50 

The  reaction  of  sulfuric  acid  and  the  simpler  gaseous  olefines  has 
recently  become  a  matter  of  industrial  interest  since  the  alkyl  sulfates 
may  be  saponified  or  hydrolyzed  by  steam  to  the  corresponding  alco- 
hols. As  first  described  by  Faraday  51  in  1827,  the  absorption  of 
ethylene  by  concentrated  sulfuric  acid,  with  the  formation  of  ethyl 
hydrogen  sulfate,  is  not  rapid  below  160°  and  according  to  Butlerow  52 
the  absorption  is  rapid  at  160°-170°.  The  question  of  an  industrial 
synthesis  of  alcohol  from  gases  containing  ethylene  was  investigated  in 
1855  by  Berthelot 53  and  later  by  P.  Fritzsche  n4  who  states  that  100 
kilos  of  concentrated  acid  are  required  to  produce  18  kilos  of  alcohol. 
The  chief  difficulties  have  been  the  handling  and  re-concentration  of 
relatively  large  quantities  of  sulfuric  acid  and  loss  of  acid  by  oxidation 
and  charring  of  other  olefines,  which  were  not  completely  removed 
prior  to  the  absorption  of  ethylene.  One  patentee  claims  that  vana- 
dium or  uranium  salts  facilitate  the  absorption  of  ethylene.55  Ferrous 
sulfate  and  cuprous  salts  are  said  to  promote  the  absorption  of  ethyl- 
ene and  under  these  conditions  56  the  gas  is  treated  with  acid  at  100°- 
120°.  Very  recently,  Bury  and  Ollander  57  have  carried  out  these  re- 
actions on  an  industrial  scale,  in  England,  and  state  that  one  ton 
of  Durham  coal  yields  sufficient  ethylene  to  produce  1.6  gallons  of  95 
per  cent  ethyl  alcohol.  After  removing  benzene  vapors  and  olefines  other 
than  ethylene,  the  gas  is  scrubbed  by  hot  95  per  cent  sulfuric  acid  and 
the  resulting  ethyl-hydrogen  sulfate  is  hydrolyzed  by  steam.  Since 

"Delepine  &  Ville,  Bull.  Soc.  chim.  27,  673   (1920). 

"Faraday,  Phil.  Trans.  IS,  118;  Regnault,  Ann.  d.  Chimie.   (2),  59   (1835). 
^Landolt,  Ber.  12.  1586   (1879). 
^Pogg,  Ann.  9,  21    (1827). 
52  Ber.  6,  196   (1873). 

63Compt.  rend.  40,  102  (1855)  ;  Ann.  Chim.   (3),  43,  385   (1855). 
<*Chem.  Ind.  20,  266   (1897)  ;  35,  637   (1912). 

55  Lattre,  French  Pat.  468,244  ;  J.  Soc.   Chem.  Ind.  1914,  953  ;  Loisy,  Compt.  rend. 
170,  50   (1920). 

66  Brit.  Pat.  152,495,  J.  800.  Chem.  Ind.  S9,  833 A   (1920). 
"Brit.  Pat.  147,360   (1914)  ;  Chem.  Weekblad.  17,  478   (1920). 


ACYCLIC  UNSATURATED  HYDROCARBONS 


167 


coal  gas  ordinarily  contains  not  over  2.5  per  cent  ethylene,  it  would  be 
reasonable  to  assume  that  such  a  process  would  be  more  successful 
with  oil  gas  or  waste  gas  from  petroleum  stills,  particularly  cracking 
or  coking  stills,  gas  from  the  latter  source  containing  5  to  6  per  cent 
ethylene.  Propylene  and  butylenes  are  absorbed  by  sulfuric  acid  at 
ordinary  temperatures  and  according  to  Hunt 58  and  Ellis  59  good  yields 
of  isopropyl  and  secondary  butyl  alcohols  are  obtainable  in  this  way. 
By  the  Ellis  process  isopropyl  alcohol  is  obtained  from  propylene  con- 
tained in  the  gases  from  Burton  stills  used  in  cracking  petroleum  oils 
to  make  gasoline.  The  gases  are  allowed  to  bubble  through  cool  sul- 
furic acid  of  specific  gravity  1.8  until  the  gravity  falls  to  1.3  or  1.4. 


^_    if 

£30 

3r 

c    *° 

<U     /$• 

C5 
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H 

jy 

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«o      /O 
C5 

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,  — 

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100° 

C 
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'i  me  in  hours, 
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4~         /O          /^         20          Z 

T'nie  in  hour^ 
J  Acid  ioa./^ 

K/4cid  97.6% 
Iff  Acid 


HI  Acid 


Absorption  of  Ethylene  in  Sulfuric  Acid  of  Different  Concentrations, 
at  50°  and  100°  C 

The  acid  liquor  is  diluted  with  water  and  polymers,  higher  alcohols, 
etc.,  allowed  to  separate.  The  diluted  liquid  is  distilled  with  steam.  A 
small  amount  of  olefines  and  propyl  ether  first  appear  in  the  distillate. 

88  Brit.  Pat.  146,956;   146,957    (1920). 

59  Oil,  Paint  d  Drug  Rep.  Dec.  20,  1920,  p.  28. 


168      CHEMISTRY  OF  THE  NON-BENZEN01D  HYDROCARBONS 

Isopropyl  alcohol  then  comes  over.  The  rate  of  absorption  of  ethylene, 
in  a  small  experimental  apparatus,  at  50°  and  100°,  is  shown  in  the 
accompanying  figures.  These  values  are  entirely  empirical  but  give  a 
good  comparison  of  the  absorption  in  acids  of  different  concentration.80 
The  reaction  of  ethylene  with  mercury  salts  is  well  known  through 
the  work  of  Hoffman  and  Sand.61  They  conclude  that  the  following 
types  of  salts  are  formed,  to  which  they  have  given  the  names  indi- 
cated, 

(1)  Ethene  mercury  salts,  CH2CH.HgX 

(2)  Ethanol  mercury  salts,  CH2OH 


CI 


(3)  Ethyl  ether  mercury  salts,  XHgC2H4OC2H4HgX 

(4)  Polymerized  ethene  mercury  salts  (C2H3HgX)n 

They  proposed  the  theory  of  the  initial  formation  of  CH2X 

CH2HgX,  . 

which  by  decomposing  with  loss  of  HX  would  give  ethene  compounds, 
or  by  reacting  with  water  ethanol  salts.  Hydrochloric  acid  decom- 
poses all  four  types,  liberating  ethylene. 

Sand 62  later  expressed  the  opinion  that  only  two  series  of  com- 
pounds are  formed  and  stated  that  the  fourth  class,  polymerized  ethene 
mercury  compounds,  did  not  exist.  Later  writers  have  confirmed  this 
view.63  Manchot 64  has  shown  that  the  ethanol  compound  C2H5OHgCl 
is  monomolecular.  In  view  of  the  ease  with  which  cold  dilute  hydro- 
chloric acid  liberates  ethylene  from  this  ethanol  compound,  not 
CH3CH2OH,  as  the  Sand  structure  would  lead  one  to  expect,  Manchot 

OH 
favors  the  structure  C2H4Hg<         the  ethylene  group  being  held  in 

Cl, 

combination  in  some  manner  analogous  to  the  way  CO  is  combined 
with  cuprous  chloride.  Manchot  explains  the  stability  of  the  mercury 
ethanol  compound  towards  nitric  and  acetic  acids  and  its  reactivity 
to  hydrochloric  acid  by  the  theory  that  mercuric  chloride  is  capable 
of  forming  the  double  compound,  HgCl2.2HCl.  The  equations  for  its 
decomposition  by  HC1  would  then  be  expressed  as  follows: 

80  Plant  and  Sidgwick,  J.  Soc.  Chem.  Ind.  1921,  14T. 

"Ber.  S3,  1340,   2692    (1900)  ;  S+,   1385    (1901). 

«*Ber.   34,   1385    (1901). 

M  Manchot,  Ann.  430.  174   (1920). 

"Loc.  cit. 


ACYCLIC  UNSATURATED  HYDROCARBONS  169 

OH 

(1)  C2H,Hg<        +  HC1  ±9  C2H4HgCl2  +  H2O 

Cl 

(2)  C2H4HgCl2  +  2HC1  ±9  HgCl2,  2HC1  +  C2H4 

The  constitution  of  these  compounds  can  hardly  be  regarded  as  defi- 
nitely determined. 

Curme  65  has  described  a  method  of  separating  ethylene  in  a  pure 
condition  from  gas  mixtures,  which  consists  in  absorbing  the  ethylene 
in  a  solution  containing  a  mercury  salt,  such  as  mercuric  sulfate,  and 
subsequently  heating  the  solution  to  expel  the  ethylene. 

CH2HgOAc 

With  mercuric  acetate  in  methyl  alcohol  the  ether    I  is 

CH2OCH3 

formed.66  Manchot  and  Brand  67  state  that  ethylene  forms  a  double 
compound  with  cuprous  chloride.  A  double  compound  with  platinum 
chloride,  C2H4Ptd2,  is  known,68  and  concentrated  aqueous  ferrous 
bromide  forms  the  crystalline  compound  C2H4FeBr2.2H20.  Hender- 
son and  Gangloff69  isolated  double  compounds  with  anhydrous  alu- 
minum chloride  (from  absolute  alcohol)  having  the  formula  A1C13. 
O2H4.2C2H5OH  and  A1C13 .  C2H4 .  CH3OH .  H20. 


Propylene  and  Substituted  Propylenes 

The  best  laboratory  method  for  the  preparation  of  propylene  is  the 
decomposition  of  isopropyl  alcohol  by  passing  over  aluminum  phos- 
phate or  kaolin  at  about  300°. 70  It  is  liquid  under  7  to  8  atmospheres 
pressure  and  would  probably  be  industrially  valuable  in  this  form. 
Propylene  forms  propanol  mercury  salts  analogous  to  those  of  ethyl- 
ene; Curme71  describes  the  use  of  ethanol  salts  to  separate  pure  ethyl- 
ene from  inert  gaseous  diluents  but  the  similar  treatment  of  gaseous 
mixtures  containing  propylene  has  not  been  described.  The  source  of 
propylene  utilized  by  Ellis  for  the  preparation  of  isopropyl  alcohol 
by  means  of  the  sulfuric  acid  esters,  is  oil  gas  or  petroleum  still  gas. 
Propylene  may  be  separated  from  ethylene  almost  quantitatively  by 
means  of  sulfuric  acid  (see  above). 

65  U.   S.  Pat.  1,315,541    (1919). 

"Schoeller,  Schrauth  &  Essers,  Bcr.  tf,  2864   (1913). 

"Ann.  370,  286   (1909). 

^Birnbaum,  Ann.  195,  69   (1868)  ;  Zeise,  Pogg.  Ann.  21,  497,592;  40,  234   (1837). 

69  J.  Am.  Chem.  Soc.  38,  1382   (1916). 

70  Senderens,  Compt.  rend.  iy,,  1110   (1907).     The  necessary  isopropyl  alcohol  may 
be  prepared  by  the  reduction  of  acetone  by  sodium, 

71  U.   S.  Pat.   1,315,541. 


170      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

The  chemical  properties  of  propylene  are  of  interest  as  showing 
the  marked  difference  in  chemical  behavior,  as  compared  with  ethylene, 
due  to  the  introduction  of  a  methyl  group  in  ethylene.  Whereas  ethyl- 
ene passed  through  98.1%  sulfuric  acid  at  70°  gives  an  increase  in 
weight  in  2.5  hours,  of  only  2.27  per  cent,  propylene  at  a  much  lower 
temperature,  25°,  in  the  same  apparatus  and  using  97%  sulfuric  acid, 
showed  a  gain  in  weight  of  50  per  cent  in  two  hours.72  Propylene  re- 
acts with  hypochlorous  acid,  to  form  the  two  chlorohydrines,  more 
rapidly  than  ethylene,  and  in  contrast  with  ethylene  is  absorbed  by 
concentrated  hydriodic  acid  in  the  cold;73  it  is  also  absorbed,  though 
less  rapidly,  by  concentrated  hydrochloric  and  hydrobomic  acid. 

The  derivatives  of  propylene  have  been  the  despair  of  those  who 
have  sought  to  formulate  simple  rules  for  the  addition  of  other  sub- 
stances to  the  olefine  group.  Usually  these  rules  have  been  based  upon 
ideas  of  electrical  polarity  and  an  arrangement  of  the  additive  sub- 
stance which  would  supposedly  satisfy  best  the  balance  of  the  forces 
of  attraction  and  repulsion.  A  few  examples  will  suffice  to  show  the 
difficulty  of  forming  generalizations  which  will  hold  true  in  this  simple 
series.  In  reactions  where  two  substances  are  formed  the  *  indicates 
the  principal  product.74 

i    TTT^T*  ^  3   OHJCHjC.HBr.Cl 

*|  CH3CHBr.CH2Cl 


CH3CC1  =  CH2  +  HI >  CH3CC1I.CH3 

CH3CC1  =  CH2  +  HBr >  CH3CC1 .  Br .  CH3 

___      S   CH,Cl.CH0CH,Br  * 

'  (  CH2Cl.CHBr.CH3 
dark 

CH3CH  =  CHC1  +  C12 >  CH2C1 .  CH  =  CHC1 

light 
CH3CH  =  CHC1  +  C12  -       — >  CH3CHC1 .  CHC12 

dark 
CH3CC1  =  CH2  +  C12  -      — >  CH2C1 .  CC1 .  =  CH2 

CH2C1 .  CC1  =  CH2  +  HC1  -        -*  CH2C1 .  CC12CH3 

rTr  rTT  _  PTTp>r   ,   TTR  5   CH3CHBr .  CH2Br  * 

*  I  CH3CH2CHBr2 

CH3C .  Br  =  CH2  +  HBr  -        -*  CH3CBr2CH3 

-PTT  -LTTR  i   CH2Br.CHBr,CH3 

—  ^     i     -"-t5"  ^   )     r^TT  T>T^    r^TT  OTT  "R*, 

(    ^yXigJor .  oxi0v_yXi2r>r 

"Plant  &  Sidgwick,  J.  Roc.  Chem.  Jnd.  W,  17  T.   (1921). 

"Butlerow,  Ann.  Itf,  275   (1868)  ;  Michael,  J.  prakt.  Chem.   (2).  60,  445    (1899). 

"Reboul,  Ann.  Chim.   (5)   l|,  461   (1878)  ;  Michael,  Ber.  39,  2787   (1906). 


ACYCLIC  UNSATURATED  HYDROCARBONS  171 

p(3'-dichloro-n-propyl  sulfide,  analogous  to  mustard  gas,  has  been 
described  by  Coffey,75  who  obtained  it  easily  from  propylene  chloro- 
hydrin  by  means  of  Clarke's 76  modification  of  Victor  Meyer's  meth- 
od.77 Coffey  was  unable  to  make  the  dichloro  sulfide  from  sulfur  chlo- 
ride and  propylene  although  in  the  case  of  ethylene  the  results  leave 
little  to  be  desired.  With  propylene,  condensation  to  dark  colored 
semi-solid  material  results,  when  the  reaction  is  carried  out  at  50°  to 
60°.  - 

The  Butylenes  and  Amylenes:     There  are  three  butylenes,  i.  e., 

CH3 
CH3CH2CH  =  CH2,         >C  =  CH2  and  CH3GH  =  CHCH3,  the  lat- 

CH3 
ter  hydrocarbon  being  known  in  cis  and  trans  form,78 

HC.CH3  HC.CH3 

HC.CH3  CH3C.H 

cis,  boiling-point  1  to  1.5°  trans,  boiling-point  2.5° 

When  primary  or  secondary  butyl  alcohol  or  the  corresponding 
halides  are  decomposed,  all  three  butylenes  are  formed.79  The  diffi- 
culty of  preparing  pure  olefines  has  repeatedly  been  emphasized  in 
these  pages.  The  butylenes  occur  in  oil  gas,  in  the  light  liquid,  con- 
densed under  pressure,  from  Pintsch-gas,  and  in  the  fore  runnings  of 
the  distillation  of  crude  benzene,  particularly  whe?^  made  by  low  tem- 
perature carbonization  of  coal  or  from  water  gas  tar.  The  butylenes 
are  not  at  present  utilized  industrially.  Their  physical  properties  are 
very  imperfectly  known  but  their  boiling  points,  as  recorded,  are  as  fol- 
lows, 

Butene-  ( 1 ) ,  boiling-point    —  5° 

Butene-(2),        "         "      cis  +  1  to  1.5°;  trans +  2.5°. 

Isobutylene,        "         "      —6°. 

Isobutylene  can  readily  be  prepared  by  dropping  tertiary  butyl 
iodide  into  boiling  water,  the  hydriodic  acid  being  retained  by  the 
water.81 

76  J.  Ghent.  Soc.  119,  94   (1921). 

76  J.  Chem.  Soc.  101,  1583   (1912). 

77  The  writer  experimented  with  this  method,  in  cooperation  with  the  U.  S.  Chem- 
ical War  Service  in  1917  and  1918,  in  the  effort  to  utilize  the  ethylene  and  propylene 
in  oil  gas.     The  yields  of  the  dichloro  sulfide  are  good,  in  the  case  of  propylene,  but 
the  product  is  much  less  toxic  than  the  ethylene  derivative. 

78  Wislicenus,  Ann.  313,  228   (1900). 

78  Faworski,  J.  prakt.  chem.  (2),  42,  153  (1890);  Senderens,  Compt.  rend.  144, 
1110  (1907)  ;  Newman,  Can.  Chem.  J.  1920,  47  and,  King,  J.  Chem.  Soc.  1919,  1404, 
describe  the  catalytic  decomposition  of  n. butyl  alcohol  to  butylene,  which  is  then 
treated  with  80%  sulfuric  acid  to  obtain  secondary  butyl  alcohol,  which  in  turn  may 
be  catalytically  dehydrogenated  to  obtain  methyl  ethyl  ketone. 

80  Wislicenus,  loc  cit. 

81Nef,  Ann.  318,  23  (1901)  ;  Cf.  Ipatiev,  Ber.  40,  1829  (1907). 


172      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

Isobutylene  is  rapidly  dissolved  by  70  per  cent  sulfuric  acid  in  the 
cold;  when  such  a  solution  made  up  with  50  per  cent  acid  is  warmed 
to  100°  di-isobutylene  C8H16  is  formed,  and  when  acid  of  stronger 
concentration,  80  per  cent,  is  employed  tri-isobutylene  is  formed,  illus- 
trating a  very  general  behavior  of  olefines,  i.  e.,  that  the  more  con- 
centrated the  acid  the  further  the  polymerization  proceeds.82 

The  butylenes  form  characteristic  crystalline  nitrosates,  or  rather 
6is-nitrosates,  when  nitrogen  peroxide  is  passed  into  cold  ether  solu- 
tions;83 reduction  of  these  nitrosates  yields  the  corresponding  diamines. 
Isobutylene  reacts  with  acetyl  chloride  in  the  presence  of  zinc  chloride 
to  form  a  chloroketone.84 

CH3  CH3 

>  C  =  CH2  +  CH3COC1 >         >  CC1 .  CH,COCH3 

CH3  CH3 

which  decomposes  on  heating  to  mesityl  oxide.  The  above  reaction 
is  analogous  to  the  reaction  between  ethylene  and  benzoyl  chloride  in 
the  presence  of  anhydrous  aluminum  chloride,  discovered  by  Norris 
and  Couch.85  As  noted  in  connection  with  the  action  of  sulfuric  acid  on 
olefines,  the  butylenes  and  amylenes  are  much  more  reactive  than  their 
higher  homologues,  and  it  is  therefore  probable  that  in  the  presence 
of  aluminum  chloride  the  rate  of  polymerization  may  greatly  exceed 
that  of  condensation  with  other  substances  as  in  Norris's  reaction. 
Very  probably  the^dgher  olefines  such  as  the  decylenes  will  give  bet- 
ter yields  of  condensation  products,  in  the  presence  of  aluminum  chlo- 
ride, than  butylene-  or  amylenes. 

The  amylenes  have  probably  been  more  thoroughly  studied  than 
any  of  the  olefines  with  the  exception  of  certain  of  the  terpenes.  This 
is  perhaps  to  be  explained  by  the  availability  of  the  raw  materials, 
amyl  alcohol  and  petroleum  pentane.  Of  the  five  possible  amylenes, 
four  are  definitely  known  but  pentene-(l)  certainly  never  has  been 
prepared  in  a  pure  state  and  it  is  doubtful  if  the  material  supposedly 
isolated  by  Brochet,86  from  the  distillate  of  bog  head  coal,  contained 
any  of  this  hydrocarbon  at  all.  It  is  also  doubtful  if  pentene-(2)  has 

82Butlerow,  Ann.  180,  247  (1876)  ;  189,  48  (1877)  ;  Ber.  12,  1482  (1879)  ;  Brooks 
&  Humphrey,  J.  Am.  Chem.  Sac.  JfO,  822  (1918). 

83  Ssiderenko,  Chem.  Zentr.  1907,  I,  399. 

"Kondakow,  J.  Russ.  Phys.-Cliem.  Roc.  26}  12   (1894). 

85  J.  Am.   Chem.   Soc.    >$,  2329    (1920). 

88  Bull.  chim.  &  Phys.  (3),  7,  567  (1892)  ;  Wurtz,  Ann.  148,  136  (1868),  and  Wag- 
ner &  Saizew,  Ann.  179,  304  (1875),  attempted  to  prepare  this  hydrocarbon  by  the 
reaction  of  allyliodide  and  zinc  ethyl ;  reaction  of  magnesium  ethyl  bromide  and  ally! 
bromide  should  yield  this  hydrocarbon  in  a  pure  state,  analogous  to  the  preparation 
of  hexene-(l)  by  Brooks  and  Humphrey,  J.  Am.  Chem.  Soc.  40,  822  (1918).  When 
this  hydrocarbon  is  prepared  its  boiling  point,  by  analogy  from  the  hexenes,  will 
probably  be  found  to  be  below  35°  instead  of  39°-40°  as  given  by  Brochet, 


ACYCLIC  UNSATURATED  HYDROCARBONS 


173 


been  prepared  in  a  fairly  pure  condition.  It  is  idle  therefore  to  com- 
pare the  physical  properties  of  these  isomeric  amylenes.  The  most 
stable  of  the  amylenes  is  trimethylethylene  and  it  is  formed  when  any 
of  the  other  amylenes  are  prepared  at  high  temperatures.  According 
to  Ipatiev87  2-methylbutene-(3),  is  almost  quantitatively  converted 
into  trimethylethylene  by  passing  over  heated  alumina, 
CH3  CH3 

^  /"ITT    /^TT  OTT  -v  ^  O  /^TT    OTJ 

^>  \jFL  .  *utt  —  \jJLL2  —  ^  ^  —  \^±i  .  \jtt.3 

CH3  CH3 

When  ordinary  amyl  alcohol  is  passed  over  alumina  at  340°-350°  all 
three  of  the  methylbutenes  are  formed,  trimethylethylene  being  the 
principal  product.88 

CH3 


CH, 


\ 


CH.CH2CH2OH 


CH3 


\ 


CH3 
CH, 


\ 


=  CH.CH, 


CH3 
CH, 


C.CH2CH3 


CH, 


Commercial  "amylene"  is  accordingly  a  mixture  of  these  hydrocarbons 
containing  trimethylethylene  as  the  principal  constituent.    When  such 
amylene  is  treated  with  70  per  cent  sulfuric  acid  in  the  cold,  the  prin- 
cipal product  is  dimethylethylcarbinol,  boiling  at  102°. 
CH3 

C.CH2CH3        +H20 


CH2 
CH3 

( 
CH3 


=  CH.CH 


H0 


CH,. 


\ 


C.CH,CH, 


CH, 


87  Ber.  S6,  2004   (1903). 

88Senderens,  Compt.  rend.  Ill,  916  (1920). 


174      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


Sulfuric  acid  in  methyl  alcohol  and  trimethylethylene  gives  the  methyl 
ether.89 

It  is  worthy  of  note,  that  most  of  the  reactions  of  the  amylenes  are 
applicable  to  the  terpenes,  and  vice  versa.  The  chemical  behavior  of 
the  two  groups  of  hydrocarbons  is  entirely  similar,  but  the  use  of  the 
word  "hydro-aromatic"  for  the  cyclohexane  derivatives  has  probably 
done  a  great  deal  to  prevent  the  full  realization  of  the  similarity,  one 
might  say  homogeneity,  of  the  chemistry  of  the  non-benzenoid  hydro- 
carbons. For  the  purpose  of  emphasizing  this  similarity  a  number  of 
reactions  of  amylenes  and  terpenes  will  be  noted. 

(1)     Addition  of  HC1  and  HBr  (in  acetic  acid  solution). 

CH3 

C.CH2CH3 


(2)     Addition  of  nitrosyl  chloride.90  91 

CH3 


CH3 
CH3 


=  CH.CH, 
CH3 

AH 


>C  —  CH.CH3 
CH3      | 

Cl     NO 


CH3 


NOC1 


H 


/\ 


in  certain  terpenes 


NO 

'H 


89  Reychler,  CTiem.  Zentr.  1907,  I,  1125. 

80  J.  Schmidt,  Ber.  35,  3732  (1902)  ;  36,  1765   (1903). 

"Wallach,  Ann.  2+5,  245  (1888)  ;  Ber.  24,  1535  (1891). 


ACYCLIC  UNSATURATED  HYDROCARBONS  175 

(3)  Behavior  of  nitroso  chlorides.92 

Both  amylenes  and  terpenes, 
FR2C  —  CHR-|  bimolecular,  T  R2C  —  CR 

L    Cl     NO    J,  crystalline    J  Cl     N.OH 

monomolecular 

(4)  Behavior   of  nitrosochlorides    and   nitrosates;    formation   of 

oximes.93 

R 
Cl 


R 

/ 

'X 

A 

H,C 

C  =  N.OH. 

x\ 

*    "1 

1 

\ 

nitrosochloride 

CH. 

\ 


//\ 
// 


oxime 

H2C  C  =  NOH. 

nitrosate 
(5)     Behavior  of  nitroso  chlorides:  formation  of  nitrolamines.94 

R 

Cl 

V 

H2C  C  =  NOH  +  H2NR 


-i- 1 

A. 


nitrosochloride  nitrolamine 

(6)     Addition  of  N204 

amylenes—      > bimolecular  or  bis-nitrosates 

terpenes   -        — > 

"Baeyer,  Ber.  28,  1586   (1895)  ;  Ber.  29,  1078   (1896). 

93  Best  carried  out  by  heating  with  sodium  acetate  in  acetic  acid.  Wallach,  Ann. 
STU,  202  ;  379,  135. 

M  Wallach,  Ann.  241,  296  (1887)  ;  262,  327  (1891)  ;  Ann.  ttf,  253  (1888)  ;  Stf,  143 
(1906). 


176       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

(7)  Oxidation,  parallel  behavior,  e.  g.,  KMn04 

trimethylethylene >  glycol. 

terpenes  >  glycols. 

(8)  Dilute  sulfuric  acid, 

CH3  CH3 


>C  =  CH.CH3  -  >         >C.CH2CH3 
CH3  CH3      | 

OH 

terpenes  --  >  terpene  alcohols 

(9)  Concentrated  mineral  acids, 

amylenes  -  --  >  diamylenes  —    --  >  triamylenes,  etc. 
terpenes   —     --  >  diterpenes   -        --  >  trimerides,  etc. 

(10)  Action  of  zinc  chloride, 

amylenes  —      --  >  polymers 
terpenes   —     -  >  polymers 

(11)  Behavior  on  heating, 

amylenes,  rearrangement  to  more  stable  form 
chiefly  trimethylethylene, 

terpenes,  rearrangement  to  more  stable  forms, 
e.  g.,  pinenes  -       --  >  dipentene,  terpinene 
phellandrenes  -  >        "  " 

(12)  Halides,  heated  with  sodium  acetate  in  acetic  acid, 
chloropentanes  ---  >  amyl  acetate    -f-     amylenes 

bornyl  chloride  -         ->  bornyl  acetate  +  { 


Also,  the  behavior  of  the  amylenes  and  the  terpenes  to  bromine,  ozone, 
catalytic  hydrogenation,  air  oxidation,  and  many  other  reactions,  is 
very  closely  parallel. 

Pentadienes:  The  preparation  and  polymerization  of  isoprene,  pi- 
perylene  and  dimethylallene  have  been  discussed  in  the  chapter  on  poly- 
merization and  the  problem  of  synthetic  rubber.  Piperylene, 


ACYCLIC  UNSATURATED  HYDROCARBONS 


177 


CH3.CH  =  CH.CH  =  CH2,  may  be  identified  by  its  physical  proper- 
ties (noted  in  the  table  on  page  231)  and  by  its  tetrabromide,  1.2.3.4- 
tetrabromopentane,  known  in  two  stereo- isomeric  forms  (1)  crystalline 
form,  melting  point  114.5°  and  (2)  a  liquid,  distilling  at  115°-118° 
(4  mm.).95  Oxidation  of  piperylene  by  permanganate  yields  formic 
and  acetic  acid.  Harries  96  endeavored  to  prove  its  constitution  by 
means  of  its  reaction  with  ozone  but  without  success ;  it  combines  only 
slowly  with  ozone  but  the  diozonide  was  so  explosive  that  no  definite 
results  were  obtained.  Auwers 97  concludes  from  the  exaltation  of  its 
refractive  index  that  the  double  bonds  are  in  the  conjugated  position. 
The  isomer  1 .4-pentadiene,  CH2  =  CH.CH2CH  =  CH2,  is  one  of  the 
products  of  the  decomposition  of  pentamethylenediamine  nitrite  but 
it  has  only  been  isolated  in  the  form  of  its  tetrabromide,98  melting- 
point  86°-87°.  The  preparation  and  polymerization  of  isoprene  is  also 
discussed  in  connection  with  the  subject  of  synthetic  rubber.  Isoprene 
in  glacial  acetic  acid  solution  combines  with  two  molecules  of  hydro- 
gen bromide  to  form  CH2Br.CH2CBr(CH3)2,  and  with  hypochlorous 
acid  to  form  a  dichlorohydrin  melting  at  82°.  It  condenses  with  ben- 
zoquinone  when  the  two  are  heated  together  at  120°-180°,  the  product 
melting  at  234°,  and  since  it  yields  a  dioxime  and  a  tetrabromide  Euler 
and  Josephson  "  conclude  that  the  combination  has  occurred  through 
the  double  bonds  in  the  isoprene,  and  the  quinone,  the  product  probably 
having  the  following  constitution. 

*  0 


CH3— 


\/      N/\ 


\ 


— CH, 


According  to  Ostromuislenski  isoprene  may  be  estimated  when  pres- 
ent in  a  mixture  of  butylenes,  amylenes,  benzene,  etc.,  by  shaking  with 
about  ten  volumes  of  fuming  hydrochloric  acid  for  six  hours;  the  prod- 

"Magnanini,  Gazz.  Chim.  Ital.  16,  391. 
"Ann.  WO,  1    (1915). 
"  Ber.   49,  827    (1916). 
88Demjanow,  Ber.  40,  2590   (1907). 
"Ber.  53t  822  (1920). 


178     CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

uct  is  washed  with  cold  brine,  dried  over  calcium  chloride  and  distilled. 
•The  fraction  distilling  at  50°-90°  contains  butyl  and  amyl  chlorides, 
the  fraction  from  90°-130°  is  separately  collected  and  then,  the  tem- 
perature rising  rapidly  from  130°  to  142°,  the  2.4-chloro-2-methyl- 
butane  fraction  in  a  fairly  pure  condition  is  collected  at  this  tempera- 
ture. Refractionation  of  the  fraction  boiling  at  90°-130°  will  yield  a 
further  small  proportion  of  the  dichloride. 

Ole fines,  Six  to  Nine  Carbon  Atoms:  Very  few  of  the  many  pos- 
sible hexenes,  heptenes,  octenes  arid  nonenes  have  ever  been  prepared, 
but  their  properties  may  be  roughly  assumed  from  the  behavior  of  the 
impure  mixtures,  which  have  been  prepared  and  from  the  properties  of 
olefines  of  the  terpene  class,  many  of  which  have  been  carefully  investi- 
gated. Certain  hydrocarbons  of  this  series  are  incorrectly  described 
in  the  literature,  for  example,  hexene- (1)  boils  at  62°-63°,  and  the  hy- 
drocarbon described  by  Brochet  10°  boiling  at  67°  which  he  separated 
from  a  distillate  from  bog  head  coal,  is  probably  a  mixture  containing 
chiefly  hexene- (2),  (see  pp.  151-152).  High  temperatures,  and  many 
chemical  reagents,  particularly  acids,  cause  such  a-olefines  to  rearrange 
or  the  double  bond  to  shift  its  position.  Only  reactions  employing  low 
temperatures  and  absence  of  isomerizing  reagents  can  be  expected  to 
produce  these  a-olefines  in  any  degree  of  purity,  for  example, 

CH2CH2CH3 

Mg  <  +  BrCH2CH  =  CH2  -»  CH3CH2CH2CH2CH  =  CH2 

Br  , 

+  MgBr2 

or  von  Braun's  method  of  decomposing  trialkyl  ammonium  hydrox- 
ide.101 

The  hexene  obtained  by  treating  secondary  hexyl  iodide  (from  man- 
nite  and  HI  with  alcoholic  caustic  potash  is  a  mixture  of  hexene- 
(1)  and  hexene- (2).  Tetramethylethylene  (CH8)2C=rC(CH8)2,  is 
the  best  known  of  the  hexenes  and  is  probably  the  most  stable.  Of  the 
heptenes  only  three  are  known  in  fairly  pure  state,  and  only  two  of  the 
many  possible  nonenes  are  definitely  known.  These  hydrocarbons  have 
been  relatively  of  such  little  importance  that  they  will  not  be  described 
in  detail.  Most  of  them,  as  described,  are  obviously  impure  and  so  few 
of  the  many  possible  hydrocarbons  are  known  that  it  is  impossible  to 
learn  anything  from  a  study  of  their  physical  properties. 

™Bull.   Ghim.   &  PUys.    (3)    7,  568    (1892). 
101  Ann.  382,  22   (1911). 


ACYCLIC  UNSATURATED  HYDROCARBONS  179 

As  regards  their  chemical  properties,  it  should  be  kept  in  mind  that 
in  the  majority  of  cases  one  is  dealing  with  mixtures.  Nearly  all  of 
the  defines  of  this  series  combine  with  hydroiodic  acid  in  the  cold, 
form  nitrosochlorides  and  nitrosates  (which  have  been  definitely  de- 
scribed in  but  a'  few  cases) ,  and  behave  normally  toward  most  of  the 
reagents  affecting  olefines.  Sulfuric  acid  yields  varying  proportions 
of  polymers,  alcohols  and  alkyl  sulfuric  esters. 

None  of  the  known  chemical  reactions  of  these  olefines  offer  much 
promise  that  the  unsaturated  hydrocarbons  in  unrefined  gasoline  will 
be  utilized.  They  can  be  removed  practically  unchanged  by  extraction 
with  liquid  sulfur  dioxide  and  their  conversion  to  alcohols,  ketones  and 
acids  would  not  be  matters  of  great  difficulty.  Such  products,  if  made, 
would  be  mixtures  and,  therefore,  entirely  unsuitable  for  certain  uses, 
for  example,  perfumes,  flavoring  materials  and  pharmaceuticals. 

When  one  reviews  the  chemical  reactions  of  such  olefines,  it  is 
evident  that  these  reactions  have  been  devised  and  applied  chiefly  for 
the  purpose  of  isolation  and  identification,  or  for  their  removal  as  a 
nuisance,  as  for  example,  the  usual  method  of  refining  with  concen- 
trated sulfuric  acid.102  It  is,  therefore,  entirely  possible  that  the  dis- 
covery of  new  reactions  will  render  these  petroleum  olefines  industrially 
valuable.103 

Octadienes:  Conylene,  C8H44.  By  distilling  the  ammonium  base 
obtained  by  exhaustive  methylation  of  coniine,  an  octadiene  is  ob- 
tained boiling  at  126°  (738  mm.).  When  benzoylconiine  is  treated 
with  phosphorus  pentachloride  1 . 5-dichlorooctane  is  obtained.104 

2.5-Dimethylhexadiene-(l.5)  105  is  of  interest  as  illustrating  a 
property,  quite  general  among  dienes  of  eight  or  more  carbon  atoms,  of 
forming  an  oxide,  the  anhydride  of  the  2 . 5-diol,  when  treated  with  70 
per  cent  sulfuric  acid.  This  substance  also  illustrates  the  labil  char- 
acter of  the  a-olefine  or  >  C  =  CH2  group,  being  converted  into  diiso- 
crotyl  by  the  action  of  alcoholic  alkali, 

102  That  large  proportions  of  the  olefines  remain  in  the  refined  oil  as  polymers,  has 
previously  been  pointed  out. 

103  Tne  writer  suggests  that  it  would  hardly  be  worth  while,  at  least  for  one  who 
greatly  values  his  time,  to  enlarge  our  knowledge  of  the  many  possible  hydrocarbons 
between  pentane  and  the  terpenes  by  proceeding  along  the  old   preparative  lines,   and 
examining  the  various  derivatives  by  old  reactions,  and  measuring  the  usual  physical 
properties.      Pending  the   possible  development  of  new   reactions,   or  greatly  improved 
old  ones,  and  the  discovery  of  uses  for  such   products  as  can  now   be  made,  it  would 
seem  that  the  best  utilization  of  such  olefines  would  be  their  polymerization,  perhaps  by 
aluminum  chloride  or  zinc  chloride   to   their  much   more  stable  polymers,   of  value  as 
lubricants. 

1Mv.  Braun  &  Schmitz  Ber.  39,  4866   (1906). 

105  Pogorzelsky,  J.  Rus8.  Phys.-Chem  Soc.  SO,  977  (1898)  ;  J.  Chem.  Soc.  Abs.  1899, 
I.  785. 


180     CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

H2SO 
70% 
CH3  CH3-     — >CH. 

\  /  >C.CH2CH2C< 

C.CH2CH2.C  CH3  CH3 

CH2  CH2  CH3  CH3 

>     >C  =  CH.CH  =  C< 

KOH      CH3  CH3 

The  latter  hydrocarbon  also  yields  this  oxide  when  treated  with  70 
per  cent  sulfuric  acid.  (Oxides  containing  five  or  six  atoms  in  the  ring 
are  very  much  more  stable  than  the  three  membered  ring  oxides  such 

RCH 

as  ethylene  or  propylene  oxides       |     >0     (Cf.  Cineol.) 


CH2' 


Nonadienes:  Geraniolene,  2.6-Dimethylheptadiene-(1.5).  This 
hydrocarbon,  boiling-point  142°-143°,  is  of  interest  on  account  of  its 
relation  to  geraniol  and  citral,  and  its  conversion  to  cyclogeraniolene 
when  treated  with  65  per  cent  sulfuric  acid.  When  the  oxime  of  citral 
is  dehydrated  by  acetic  anhydride  the  nitrile  is  formed  which  readily 
yields  geranic  acid,  C9H15.C02H.  On  distillation  at  ordinary  pres- 
sure, geranic  acid  loses  a  molecule  of  C02  and  forms  "geraniolene."  108 
The  constitution  of  this  hydrocarbon  follows  from  the  structure  of 
citral  and,  if  we  accept  the  structure  of  citral  as  found  by  Barbier  and 
Bouveault  107  the  relations  between  geraniolene  and  a  and  p-cycloger- 
aniolene  are  as  follows: 

CH3 
CH3  CH3          CH3  CH2  —  C 

^C  =  CH.  CH2CH2C  -  >  C  CH 

CH3  CH2          CH3          CH2  —  CH2 

CH3 

CH3  CH  =  C 

and  >C<  >CH2 


10«Tiemann  &  Semmler,  Ber.  26,  2708   (1893). 
107  Compt.  rend.  122,  393   (1896). 


ACYCLIC  UNSATURATED  HYDROCARBONS  181 

Tiemanns'  conclusions108  as  to  the  constitution  of  geraniolene  and  the 
cyclogeraniolenes  are  confirmed  by  Crossley  and  Gilling109  by  the 
synthesis  of  the  supposed  intermediate  alcohol,  and  the  conversion  of 
the  corresponding  bromide  into  a  and  (3-cyclogeraniolene. 

CH3 
'      LlBr 


Decadienes  and  Decatrienes :  Dihydromyrcene,  2 . 6-Dimethy  locta- 
diene  (2.6).  Boiling-point  166°-168°,  D150  0.7792.110  This  hydrocar- 
bon is  obtained  by  the  partial  hydrogenation  of  ocimene  or  myrcene, 
by  means  of  sodium  and  alcohol,111  or  by  slowly  distilling  methylger- 
anic  acid.112  Like  geraniolene  it  is  converted  into  a  cyclic  hydrocarbon 
by  sulfuric  acid  (in  acetic  acid).113  Kishner's  method  of  converting 
aldehydes  and  ketones  to  hydrocarbons  114  converts  citral  to  an  isomer 
of  dihydromyrcene,  boiling-point  164.5°.  Kishner's  method  reduces  the 
carbonyl  group  to  — CH2 —  without  affecting  the  ethylene  bonds 
present. 

CH3 

>C  =  CH.CH2CH2C  =  CH.CHO 
CH3 

CH3 

CH3 

>      >  C  =  CH .  CH2CH2C  =  CH .  CH, 

CH3  | 

CH3 

108  Ber.  31,  816   (3898)  ;  S3,  3711   (1900). 

109  J.    Chem.   Soc.   97,   2218    (1910).     The   above   structures   are   also   confirmed   by 
the  work  of  Wallach,  Ann,  32$,  97   (1902)    but  are  not  accepted  by  Harries  and  Turk, 
Ann.  3$3,  331,  362   (1905). 

110Enklaar,  Kec.  trav.  cMm.  26,  164    (1907). 
111  Semmler,  Ber.  3jf  3126   (1910). 
U2Tiffeneau.   Compt.  rend.  U,6,  1154    (1908). 
113  J.  Russ.  Phys.-Chem.  Soc.  tf,  951   (1911), 
u*Enklaar,  Ber.  41,  2083  (1908). 


182      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


'Myrcene,  Ocimene  and  Alloocimene:  C10H16.  These  hydrocarbons 
are  isomeric  decatrienes,  two  of  the  double  bonds  being  in  conjugated 
positions.  All  three  hydrocarbons  yield  2 . 6-dimethyl  octane  on  hydro- 
genation.115  They  are  sometimes  called  "aliphatic  terpenes"  perhaps 
because  of  their  empirical  formulae  C10H16  and  the  fact  that  myrcene 
and  ocimene  are  constituents  of  essential  oils.  Myrcene  was  discovered 
by  Power  and  Kleber  116  in  oil  of  bay,  Pimento,  acris  (Myrcia  acris) , 
one  of  the  myrtaceae,  and  thus  named  by  them.  It  also  occurs  in  oil 
of  hops  117  and  in  oil  of  verbena,  Lippia  citriodoro.*18  The  physical 
properties  of  these  three  hydrocarbons  are  as  follows: 
Myrcene 


Power  &  Kleber 
Semmler119 
Enklaar  12° 

Ocimene 

Van  Romburgh  m 
Enklaar122 
Allo-Ocimene 

Auwers  &  Eisenlohr123 
Enklaar122 


Boiling  -Paint 

Density 

15° 

167° 

:  67-38°  20mm. 

0.8023 

171-172° 

:  67-80°  20mm. 



166-168° 

0.8013 

Density 

15° 

.176-178° 

:  73-74°  21mm. 

0.801 

81°  30mm. 

0.8031 

188' 


:  81°  12mm. 


0.8119 
0.8133 


15.6C 


n 

D 

1.4673 
1.4673 
1.4700 

n 

D 

1.4861 
1.4857 


1.54558 
1.5447 


Myrcene  and  ocimene,  on  partial  hydrogenation,  yield  the  same  di- 
hydromyrcene (dihydromyrcene  tetrabromide  melting-point  88°),  and 
of  the  two  original  hydrocarbons  myrcene  is  much  more  rapidly  resini- 
fied.  Enklaar  proposed  the  following  structures  for  myrcene,  ocimene 
and  dihydromyrcene. 

CH3 

>C=CH .  CH2CH2C— CH=CH2 
CH, 


myrcene 


;i 


H 


CH 
CH 


>C=CH  .  CH2CH,C=CH  .  CH. 

" 


CH3  t 

>C=CH  .  CH2CH=C—  CH=CH 
CH3  | 

C 


CH3 

reaction-product 


H 


ocmene 


««  Enklaar,  Ber.  LI,  2083   (1908). 
™Pharm.  Rev.   (New  York),  is.  61   (1895). 
117  Semmler  &  Mayer,  Ber.  44,,  2009  (1911). 
118Barbier,  Bull.   Soc.   Chim.    (3),   25,   691    (1901). 

119  Ber.  3k,  3126    (1901). 

120  Rec.  trav.  chim.  26,  157   (1907)  ;  Schimmel  &  Co.  Semi-Ann.  Rep.  1906,  I,  109. 

121  Chem.  Zcntr.  1901,  I,  1006. 

123  Rec.  trav.  Chim.  26,  157   (1907)  ;  Schimmel  &  Co.  Semi^Ann.  Rep.  1906,  I,  109. 
123  J.  prakt.  Chem.   (2)  81,,  37   (1911). 


ACYCLIC  UNSATURATED  HYDROCARBONS  183 

Ocimene  derives  its  name  from  its  presence  in  the  essential  oil  of 
Gcimum  basilicum. 

Allo-ocimene  was  thought  to  be  a  geometrical  isomer  of  ocimene, 
being  obtained  from  this  hydrocarbon  by  heating.  Enklaar12*  later 
studied  the  ozonides  and  the  resulting  decomposition  products  of  these 
hydrocarbons  and  concludes  that  allo-ocimene  is 

CH3 

>C  =  CH.CH  =  CH.C  =  CH.CH3 
CH3 


CH3 


This  structure  having  all  three  ethylene  bonds  in  conjugated  positions, 
as  in  n  .  hexatriene,  accounts  for  the  high  refractivity  of  this  hydro- 
carbon. 

Both  ocimene  and  myrcene  yield  alcohols,  ocimenol  and  myrtenol, 
on  treating  with  acetic  acid  and  a  trace  of  sulfuric  acid,  according  to 
Bertram  and  Walbaum.  Barbier  125  believes  myrcenol  to  be  different 
from  linalool,  and  Enklaar  noted  the  following  constants:  Boiling- 
point  99°  (10  mm.),  d150  0.9032,  nl5°  1.4806,  phenylurethane  melting- 

point  68°.  Ocimenol  gives  a  phenylurethane  melting  at  72°.  Enklaar  is 
of  the  opinion  that  myrcene,  ocimene  and  allo-ocimene  are  not  obtain- 
able in  a  state  of  purity,  an  opinion  held  by  Wallach  with  regard  to 
the  terpinenes  and  phellandrenes.  The  instability  of  the  former  hy- 
drocarbons probably  accounts  for  the  fact  that  the  physical  constants 
of  the  myrcene  investigated  by  Lebedew  and  Mereshkowski  126  was 
found,  after  "repeated  purification,"  to  be  quite  different  from  the  con- 
stants observed  by  others.127 

Other  Derivatives  of  2  .  6-Dimethyloctane. 

The  Citral  Group:  Several  well-known  alcohols  and  aldehydes  be- 
long to  this  group.  Their  occurrence  in  essential  oils  is  very  wide  and 
includes  a  very  large  number  of  plant  species.  Many  of  the  most  valu- 
able essential  oils  owe  their  fine  aroma  chiefly  to  substances  of  this 
group,  for  example,  the  essential  oils  of  the  rose,  Rosa  damascena  and 
Rosa  centijolia,  lavender  and  orange  blossoms.  Some  of  the  cheaper 
oils  such  as  lemon  grass,  citronella  and  palmrosa  oils  are  used  as  raw 


.  trav.  cJiim.  36,  215   (1916). 

125  Bull.  Soc.  chim.    (3)   25,  687    (1901). 

128  J.  Russ.  Phys.-Chem.  Soc.  !£,  1249    (1913). 

127  The  polymerizing  action  of  metallic  sodium  on  conjugated  dienes  is  now  well 
known  ;  such  hydrocarbons  give  a  brown  resinous  deposit  after  repeated  distillation 
over  sodium. 


184      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

materials  for  the  isolation  of  certain  constituents  such  as  citral  and 
geraniol,  which  are  further  utilized,  as  in  the  manufacture  of  ionone 
from  citral.  The  chemical  behavior  of  these  alcohols  and  aldehydes 
has  been  well  established  but  in  most  cases  it  has  been  impossible  defi- 
nitely to  distinguish  between  the  groups 

CH3  CH3 

C  =  CHR  and  C.CH2R. 

CH3  CH2 

Instead  of  outlining  the  historical  development  of  the  subject,  the  gen- 
eral relationships  of  the  substances  in  this  group  will  be  indicated,  fol- 
lowed by  a  description  of  the  individual  substances  and  some  of  their 
more  important  reactions. 

The  chemical  behavior  and  constitution  of  substances  in  the  citral 
series  is  intimately  associated  with  methylheptenone,128  or,  as  Tiemann 
and  Semmler129  showed  it  to  be,  2-methylheptene-(2)-one-(6),  (CH3)2 
=  CH.CH2CH2COCH3.  A  little  later,  Verley  13°  confirmed  this  struc- 
ture by  synthesis.  Oxidation,  first  by  Wagner's  method,  using  cold 
dilute  permanganate,  followed  by  chromic  acid,  yields  acetone,  and 
levulinic  acid. 

CH3         : 

>C  =  CH.CH2CH2COCH3 >  (CH,),CO  +  CH0COCH3 

CH3         :  | 

:  CH2C02H 

On  boiling  an  aqueous  solution  of  potassium  carbonate  with  citral 
methylheptenone  and  acetaldehyde  are  formed,  and  on  oxidizing  with 
chromic  acid  methylheptenone  is  also  produced.  The  empirical  for- 
mula of  citral  is  C10H160  and  its  chemical  behavior  and  physical  prop- 
erties indicate  that  it  is  an  aldehyde  containing  two  double  bonds.  If 
methylheptenone  condensed  with  acetaldehyde,  splitting  off  a  molecule 
of  water  as  in  the  condensation  of  acetaldehyde  to  croton  aldehyde,  or 
acetone  to  mesityl  oxide, 

CH3  CHO  +  CH3CHO >  CH3CH  =  CH .  CHO 

128  Methylheptenone    is    usually    associated    with    citral,    and    is    a    constituent    of 
lemon  grass,  lemon,  palmarosa  and  linaloe  oils.     It  is  best  prepared  by  boiling  a  10% 
solution    of    potassium    carbonate    with    citral,    Verley,    Bull.    S&c.    chim.    (3)    17,    176 
(1897).     Its  boiling-point  is  173°-174°  ;  density  20°  0.8602.     Hydrogen  in  the  presence 
of  nickel  at  180°-190°  saturates  only  the  double  bond  ;  sodium  and  alcohol  reduces  the 
ketone   group    forming   methyl   heptenol.      It    reacts    normally    with    alkyl    magnesium 
halides. 

129  Ber.  28,  2115,   2126    (1895). 
wBull.  Soc.  chim.  17,  192   (1897). 


ACYCLIC  UNSATURATED  HYDROCARBONS  185 

CH3  CH3 

>  CO  +  H2CH .  COCH3 >         >  C  =  CH .  COCH3 

CH3  CH3 

the  result  would  be  citral.  Such  a  reaction  would  be  the  reverse  of 
the  hydrolytic  reaction  brought  about  by  aqueous  .potassium  carbonate. 

CH3  CH3 

>C  =  CH.CH2CH2C  =  CH.CHO ->  >C  =  CH.CH2CH2C  =  0 
CH3  |  CH3  | 

CH3  CH3 

citral  +  CH3CHO 

That  this  is  the  structure  of  citral  is  indicated  by  the  synthesis  of 
geranic  acid  from  methylheptenone  131  and  the  conversion  of  geranic 
acid  to  citral  by  heating  its  calcium  salt  with  calcium  formate.132 
Methylheptenone  and  iodoacetic  ester  condense  in  the  presence  of  zinc 
to  give  the  hydroxy  acid  and  heating  this  with  acetic  anhydride  yields 
geranic  acid. 

CH3 

>C  =  CH.CH,CH2C  =  O  +  CH2I.C02R > 

CH3  | 

CH3 

CH3  OZnl 

->         >C  =  CH.CH2CH2C<  >  hydroxy  acid 

CH3  I      CH2C02H 

CH3 

CH3 

>         >  C  =  CH .  CH2CH2C  =  CH .  CO.H > 

CH3 

CH3 

CH3 

>C  =  CH.CH2CH2C  =  CH.CHO 
CH3 

CH3 

citral 

Tiemann  133  discovered  that  purified  natural  citral  yields  mainly 
a  semicarbazone  melting  at  164°,  and  from  the  mother  liquors  of  these 
crystals  a  second  semicarbazone  melting  at  171°  was  isolated;  mixtures 
of  the  two  melt  as  low  as  130°.  The  aldehyde  yielding  the  low  melting 

131Barbier  &  Bouveault,  Compt  rend.  122,  393    (1896). 

132  Tiemann,  Ber.  SI,  827   (1898). 

134 Ber.  SI,  3331   (1898)  ;  S2,  115   (1899)  ;  53,  877  (1900). 


186      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

semicarbazone  was  designated  "citral  a"  and  the  other  "citral  b."  Cit- 
ral  a  condenses  more  readily  with  cyanacetic  acid,  forming  a  citry- 
lidene  cyanacetic  acid  melting  at  122°  and  the  corresponding  deriva- 
tive of  citral  b  melts  at  94°-95°.  Tiemann  considered  these  isomeric 
crystalline  derivatives  as  geometrical  isomers  and  Zeitschel 134  states 
that  citral  a  and  citral  b  probably  correspond  to  the  geometrically 
isomeric  alcohols  geraniol  and  nerol. 

Me2C  =  CH .  CH2CH2C  —  CH3  Me2C  =  CH .  CH2CH2C  —  CH3 


—  CH,OH.  HC.CHO 


geraniol  citral  a 

Me2C  =  CH .  CH2CH2C  —  CH3  Me2C  =  CH .  CH2CH2C  —  CH3 

II  ->  II 

HO.H2C  —  C  —  H.  OHC  —  C  —  H 

nerol  citral  b 

Citral  a  and  citral  b  have  practically  the  same  chemical  proper- 
ties 135  and  their  physical  properties  differ  only  very  slightly.  As  a 
rule,  the  boiling-points  of  such  geometrical  isomers  differ  only  very 
slightly,  for  example,  the  two  (3-butylenes,  and  dibromobutylenes 

HC  —  CH3       boiling-point  HC  —  CH3    boiling-point 

HC  — CH3     -f  1°  to  1.5°  CH3  — C  — H    +  2°  to  2.7° 

Br  —  C  —  CH3       boiling-point  Br  —  C  —  CH3     boiling-point 

II  II 

Br  — C  — CH3       146°-146.5°         CH3  — C  — Br  149°-150° 

That  small  differences  in  structure  may  greatly  affect  the  melting 
point  has  previously  been  pointed  out,  and  the  different  melting  points 
of  certain  derivatives  of  these  isomeric  citrals  is  a  case  in  point.  Con- 
version of  citral  a  to  citral  b  and  vice  versa  takes  place  readily,  and, 
according  to  Bouveault,136  alkalies  convert  a  to  b.  Ordinary  natural 
citral  gives  nearly  pure  condensation  products  of  citral  a. 

Further  confirmation  of  the  above  relationship  of  geraniol  and  nerol 
is  found  in  the  behavior  of  these  two  alcohols  on  oxidation,  first  by 
dilute  permanganate  thus  oxidizing  the  double  bonds  to  glycols,  and 
followed  by  oxidation  with  chromic  acid.  Both  alcohols  yield  the  same 
oxidation  products  and  in  the  same  proportions,  i.  e.,  acetone,  levulinic 

134  Ber.  39,   1780    (1906). 

185  Tiemann,   Ber.  S3,  877    (1900). 

w  Bull.  Soc.  chim.  (B),  21,  423. 


ACYCLIC  UNSATURATED  HYDROCARBONS 


187 


Boiling-point   

«  « 

Specific  gravity , 

Refractive  index 

Diphenylurethane,  M.  P. 
Tetrabromide,  M.  P 


acid  and  oxalic  acid.137  As  in  the  case  of  the  two  citrals,  geraniol  and 
nerol  have  nearly  identical  physical  properties  but  the  melting-points 
of  some  of  their  condensation  products  differ  markedly. 

Geraniol 138  Nerol  13° 

230°  226°-227° 

..       HOMirUOmm.)  111°  (9mm.) 

0.8812  to  0.883"°  0.8813150 

1.4766  -  1.4786  1.468 

82.5°  52°-53° 

70°-71°  118°-119° 

Separation  of  geraniol  and  nerol  is  best  carried  out  by  means  of  anhy- 
drous calcium  chloride  which  forms  a  crystalline  product  with  geraniol 
but  not  with  nerol. 

According  to  a  recent  paper  by  Verley,140  citral  a  is  mainly  the  A1 
isomer.  When  it  is  boiled  with  one  per  cent  aqueous  caustic  soda 
2-methyl-A1-heptenone  is  produced,  which  when  oxidized  first  by  per- 
manganate and  then  by  chromic  acid  gives  only  traces  of  acetone, 

OH 


CH. 


CH,OH. 


\ 
/ 


C-CH,CH9CH9CO.CH, 


\ 
/ 


-CH9CH9CH,COCH, 


CH3  CH3 

This  methylheptenone  is  rapidly  converted  into  the  isomeric,  ordinary 
2-methyl-A2-heptenone,  by  warming  with  dilute  sulfuric  acid.  Verley 
therefore  favors  the  corresponding  A1  formula  for  geraniol  and  points 
out  that  this  structure  better  explains  the  conversion  of  geraniol  to 
dipentene. 


CH, 


HC. 


CH 


CH2OH 


Clf 


H 


H5 


H 


CM, 


CH, 


'"Blumann  &  Zeitschel.  Ber.  U,  2590   (1911). 

138  Bertram    &   Gildemeister,    J.    prakt.    Chem.    (2)    56,   508    (1897)  ;    Erdmann,    J. 
prakt.  Chem.  (2)  56,  3  (1897)  ;  Stephan,  ibid.,  58,  110  (1898). 
139Soden  &  Treff,  Chem.  Ztg.  27,  897    (1903). 
™Bull.  Soc.  chim.   (4),  25,  68   (1919). 


188      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

Two  ketones  occurring  in  artemisia  oil  appear  to  have  a  carbon 
structure  different  from  the  citral  group  but  these  two  isomeric  ketones 
are  supposed  to  bear  the  same  relation  to  each  other  as  the  A1  and  A2 
isomers  discussed  above.141 

As  is  indicated  in  the  foregoing  discussion  of  the  constitution  of 
citral,  the  constitution  of  geraniol  and  nerol  are  shown  by  their  rela- 
tions to  citral.  Citral  is  formed  from  geraniol  by  oxidation  with  chro- 
mic acid,142  and  reduction  of  citral  yields  geraniol.  Apparently  only 
the  groups  —  CH2OH  and  —  CHO  are  affected.  On  more  energetic 
oxidation  the  citral  first  formed  is  oxidized  as  indicated  above,  to 
methylheptenone,  acetone,  levulinic  acid,  etc.  These  relations  are, 
therefore,  expressed  by  the  following  constitutions  of  geraniol, 

CH3 

C  =  CH.CH2CH2C  =  CH.CH2OH 


CH; 
CH 


OH, 


or,  C .  CH2CH2CH2C  =  CH .  CH2OH 

CH2  '  CH3 

When  geraniol  is  heated  with  water  in  an  autoclave  to  200°  linalool 
is  formed,143  and  the  conversion  of  linalool  to  geraniol,  or  geranyl  ace- 
tate is  brought  about  by  heating  with  acetic  anhydride.144  By  warm- 
ing a  solution  of  linalool  in  toluene  with  hydrochloric  acid,  geranyl 
chloride  is  formed.145  These  changes  are  readily  understood  from  the 
structure  of  linalool  deduced  by  Tiemann  and  Semmler146  by  a  study 
of  the  oxidation  products  of  linalool.  Oxidizing  first  with  dilute  per- 
manganate, followed  by  chromic  acid  gave  acetone  and  levulinic  acid 
(equivalent  to  methylheptenone)  and  oxalic  acid. 

CH3         :  OH  .  CH3 

>C  =  CH.CH2CH2C<.    •  >         >CO  + 

CH3         :  |  .CH  =  CH2          CH3 

CH3  . 

14lAsahina  &  Takagi,  J.  Chem.  8oc.  Abs.  1921,  I.  9. 
"2  Semmler,  Ber.  23,  2966    (1890). 

143  Schimmel  &  Co.'s  Ber.  1898,  I,  25. 

144  Bouchardat,  Compt.  rend.  116,  1253  (1893).     Terpineol  is  also  formed. 

145  Tiemann,  Ber.  31,  832    (1898)  ;   Dupont  &  Labaune,   Roure-B&rtrand,  Fils.  Bull. 
1909,  II.  27;  Forster  &  Cardwell,  J.  Chem.  Soc.  103,  1338   (1913). 

148  Ber.  28,  2126  (1895). 


ACYCLIC  UNSATURATED  HYDROCARBONS  189 

C02H.CH2CH2CO  C02H 

CH3  C02H 

It  was  also  pointed  out  that  the  chemical  and  physical  properties  of 
linalool  agree  with  the  structure  of  a  tertiary  alcohol,  and  that  when 
oxidized  by  chromic  acid  direct,  to  citral,  isomerization  by  the  acid  to 
geraniol,  or  the  glycol,  first  takes  place, 

by  acid                               CrO3 
linool  -  »       geraniol  -  >      citral 

OH  OH 

CH3  I  | 

>  C  =  CH .  CH2CH2C  —  CH  =  CH, >  RC  —  CH2  —  CH2OH 

CH3  |  | 

CH3  CH3 

linalool 


»  R  _  c  =  CH.CH2OH  -      >  RC  =  CH.CHO 

CH3  geraniol  CH3     citral 

Linalool  has  recently  been  synthesized  by  Ruzicka  14T  who  employed 
a  reaction  discovered  by  Nef,148  i.  e.,  condensation  of  acetylene  with 
ketones  by  means  of  metallic  sodium.  The  first  condensation  product 
gives  good  yields  of  linalool  on  reducing  by  moist  ether  at  low  tem- 
peratures. \ 
CH3 

>C  =  CHCH2CH,C  =  CO  +  HC  =  CH 
CH3 

CH3 

CH3  OH 

>        >  C  =  CH .  CH2CH2C  < 

CH3  |      C  =  CH >  linalool 

CH3 

The  constitution  of  citronellol  and  the  corresponding  aldehyde,  cit- 
ronellal,  is  shown  by  the  following  reactions;  citral  may  be  oxidized  to 
the  corresponding  acid  geranic  acid  and  on  reducing  this  by  sodium  and 
amyl  alcohol  citronellic  acid  is  obtained;  also  the  aldehyde  citronellal 
may  be  converted  to  its  oxime  and  this,  by  loss  of  H20,  to  the  nitril, 
which  yields  citronellic  acid.  Therefore,  citronellol  is  dihydrogeraniol, 

™  Helv.  CMm.  Acta.  2,  182    (1919). 
148  Ann.  308,  264    (1898). 


190      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

and  citronellal  is  dihydrocitral.149  As  to  the  location  of  the  remaining 
double  bond  in  citronellic  acid,  citronellol  and  its  aldehyde,  the  evi- 
dence was  at  first  confusing,  but  the  facts  are  best  explained  by  the 
reduction  of  the  RC  =  CH .  COOH  group,  which  is  in  harmony  with 

CH3 

the  well  known  highly  reactive  character  of  the  >C  =  C — CO — • 
group.  The  aldehyde  citronelall  can  be  reduced  mainly  to  the  corre- 
sponding alcohol,  citronellol,  by  sodium  amalgam  in  acetic  acid.150  As 
with  the  other  substances  of  this  group,  some  doubt  remains  as  to 
whether  the  double  bond  in  citronellol  and  its  aldehyde  is  in  the  po- 
sition, shown  but  according  to  Harries151  both  isomers  are  present  in 
natural  citronellol,  i.  e.; 

CH3 

C  =  CH.CH2CH2CH.CH.CH2OH 

CH3  CH3 

and 
CH3 

C  —  CH2CH2CH2CH .  CH2CH2OH. 

CH2  CH3 

Citronellol  and  rhodinol  appear  to  be  isomers  differing  only  in  the 

CH2 

position  of  the  double  bond,  C.CH2R,  or  (CH3)2C  =  CH.R. 

CH3 

The  question  of  the  existence  of  rhodinol  has  been  the  subject  of  con- 
siderable controversy,  the  difficulty  of  deciding  such  questions  being 
that,  as  in  all  such  cases,  the  chemical  behavior  and  physical  prop- 
erties are  so  nearly  identical,  and  conversion  of  the  one  isomer  into  the 
other  takes  place  with  great  ease.  In  discussing  the  simple  aliphatic 
olefines,  such  as  hexene(l),  it  was  pointed  out  that  double  bonds  of 
the  type  RCH2CH  —  CH2  frequently  shift  their  position  very  readily, 
and  the  work  of  Verley,  noted  above,  shows  that  warming  with  dilute 
sulfuric  acid  changes  the  group 

149  Tiemann,  Ber.  SI,  2899  (1898)  ;  Bouveault,  Comvt  rend.  138,  1699   (1904). 

160  Dodge,  Am.  Chem.  J.  11,  463   (1889). 

161  Ber.  41,  287   (1908). 


ACYCLIC  UNSATURATED  HYDROCARBONS  191 

CH2 

C.CH2R  to  the  isomer  (CH3)2C  =  CH.R. 
CH3 

German  chemists  continued  to  regard  rhodinol  as  a  mixture  of  cit- 
ronellol  and  geraniol  but  Harries  152  and  his  assistants  have  shown  that 
natural  citronellbl  and  the  aldehyde  citronellal  consists  of  a  mixture 
of  the  two  isomers,  confirming  the  contention  of  Barbier,  Bouveault 153 
and  Locquin  154  as  to  the  existence  of  rhodinol.  According  to  Harries 
ordinary  citronellal,  derived  from  oil  of  citronella,  contains  approxi- 
mately 60  per  cent  "rhodinal,"  the  aldehyde  corresponding  to  rhodinol. 
Methods  of  oxidation  have  not  clearly  shown  the  structure  of  these 
isomers  but  rhodinol  appears  to  be  the  more  stable  of  the  two  alcohols. 
Both  alcohols,  in  the  form  of  their  acetates,  combine  with  hydrogen 
bromide,  and  when  this  is  removed  by  heating  with  sodium  acetate, 
rhodinol  is  the  product.  Also,  according  to  Barbier  and  Locquin,155 
citronellal  may  be  converted  into  its  oxime,  which  on  dehydrating  by 
acetic  anhydride  yields  the  nitrile,  but  the  oxime  of  the  aldehyde,  made 
by  the  oxidation  of  ^-rhodinol  or  d-rhodinol,  does  not  yield  the  nitrile 
but  acetylmenthone  oxime.  Citronellol  may  be  converted  into  rhodinol 
by  the  addition  of  water,  brought  about  by  treating  with  30  per  cent 
sulfuric  acid. 

CH2 

C .  CH2CH2CH .  CH2 .  CH2OH 

/  citronellol 

CH3  I    CH3 

CH3 

C .  CH2CH2CH2CH .  CH2CH2OH 

CH3     OH         |          CH3 
CH3 

C  =  CH .  CH2CH2CH .  CH2 .  CH2OH 

/  rhodinol   (according  to 

CH3  CH3  Barbier). 

153  Ber.  41,  2187  (1908)  ;  Ann.  410,  1   (1915). 
163  Bull.   Soc.   cMm.    (3),   23,  458, -465    (1900). 
™Compt.  rend.  157,  1114   (1913). 
158  LOG.  ait. 


192      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

Prins 156  endeavored  to  separate  natural  citronellal  into  its  two  isomers, 
by  repeated  fractional  distillation157  followed  by  repeated  fractional 
crystallization  of  the  semicarbazone  and  semioxamazone,  but  without 
success.  Prins  also  studied  the  conversion  of  citronellal  to  isopulegol, 
by  treating  with  85  per  cent  formic  acid  and  by  80  per  cent  phosphoric 
acid  but  was  unable  to  detect  the  formation  of  any  substance,  which 
could  be  derived  directly  from  rhodinal.  The  formation  of  isopulegol 
acetate  by  heating  ordinary  citronellal  with  acetic  anhydride  is  prac- 
tically quantitative,158  which,  in  the  light  of  Harries'  work,  indicates 
that  under  these  conditions  rhodinal  must  be  converted  into  its  isomer, 
true  citronellal.  Barbier  and  Bouveault  believed  that  they  had  ob- 
tained small  yields  of  menthone  from  rhodinal,  but  Tiemann  and 
Schmidt 159  were  unable  to  confirm  this.  The  ready  conversion  of  cit- 
ronellal to  isopulegol,  however,  favors  the  structure  purposed  by  Bar- 
bier  for  this  aldehyde, 


According  to  Semmler  16°  aldehydes  of  the  types  R2CH .  CHO  and 
RCH2CHO  are  converted  to  enolic  forms  by  acetic  anhydride  and  that 
in  the  case  of  citronellal  this  change  precedes  ring  formation. 

The  above  review  illustrates  how  difficult  it  is  to  distinguish  be- 
tween isomers  of  this  kind. 

Geraniol.  The  importance  of  the  alcohols  and  aldehydes  of  this 
group  to  the  essential  oil  industry  warrants  further  description  of  them 
and  their  chemical  behavior.  Geraniol  is  present  to  a  large  extent  in 
palmarosa  oil,  ginger  grass,  citronella  and  oil  of  sweet  geranium,  partly 

156  Chem.  Weekbl.  IJf,  627,  692  (1917).  The  maximum  difference  in  boiling-points 
observed  by  Prins  was  198°-200°  for  the  low-boiling  fraction  and  203°-204°  for  the 
higher  boiling  portion. 

167  Schimmel  &  Co.'s  Rep.  1910,  I,  155. 

™Schimmel  &  Co.'s  Rep.  1896,  34;  Semmler,. Ber.  42,  584,  963,  1161,  2014   (1909). 

160  Ber.  30,  38   (1897). 

160  Ber.  ^2,  584,  963,  1161,  2014   (1909)  ;  kk,  991   (1911). 


ACYCLIC  UNSATURATED  HYDROCARBONS  193 

in  the  free  state  and  partly  as  the  acetate.  In  oil  of  geranium  small 
proportions  of  the  geraniol  ester  of  tiglic  acid  are  present.161  Com- 
mercially geraniol  is  isolated  from  either  palmarosa  or  citronella  oil  by 
means  of  finely  ground  anhydrous  calcium  chloride,  the  mixture  being 
chilled  to  about  — 5°  for  several  hours.  Other  oils  are  removed  by 
means  of  petroleum  ether  and  the  crystalline  calcium  chloride  com- 
pound decomposed  by  water.  Small  percentages  of  geraniol  cannot  be 
separated  from  essential  oils  in  this  manner.  It  is  readily  identified 
by  its  diphenylurethane,162  melting-point  82°,  or  its  naphthylurethane, 
melting-point  47°-48°. 

Geranyl  chloride  is  of  particular .  interest  as  filling  a  niche  in  the 
chemistry  of  the  non-benzenoid  hydrocarbons  and  contributing  to  the 
generally  similar  chemical  behavior  of  this  whole  class  of  substances. 
Although  not  mentioned  in  Richter's  "Lexikon"  geranyl  chloride  was 
evidently  first  made  by  Jacobsen 163  and  later  by  Tiemann 164  who  pre- 
pared large  quantities  of  it  by  the  action  of  hydrogen  chloride  on 
geraniol.  Dupont  and  Labaune 165  passed  dry  hydrogen  chloride  into 
a  solution  of  geraniol  or  linalool  in  toluene  at  100°  and  noted  that 
both  alcohols  gave  the  same  chloride,  which  they  called  linalyl  chloride, 
and  Kerschbaum 166  following  Tiemann's  first  method,  made  it  by 
treating  geraniol  with  phosphorus  trichloride.  The  first  study  of  the 
chloride  and  its  reactions  was  carried  out  by  Forster  and  Cardwell,167 
who  employed  Darzen's  method,  dissolving  the  geraniol  in  pyridine 
and  treating  with  thionyl  chloride.  The  chloride  was  shown  to  be  a 
derivative  of  geraniol  rather  than  linalool  by  the  preparation  of  geranyl 
acetone,  by  the  action  of  geranyl  chloride  on  the  sodium  derivative  of 
acetoacetic  ester,  and  hydrolysis  of  the  geranyl  acetoacetate  by  barium 
hydroxide.  The  constitution  of  geranyl  acetone  is  shown  by  reference 
to  the  constitution  of  farnesol 168  and  the  work  of  Kerschbaum.169  The 
chlorine  atom  in  geranyl  chloride  is  stabilized  by  the  proximity  of  a 
double  bond,  (CH3)  C  =  CH .  CH2CH2C  =  CH .  CH2C1  but  it  reacts 


normally  with  sodium  ethoxide  to  give  the  ethyl  ether  and  with  sodium 
acetoacetic  ester  and  sodium  malonic  ester.    From  the  latter  substance 

181  Schimmel  &  Co.,  Semi-Ann.  Rep.  191S,  II,  61. 

1(82  Cf.  Parry,   "Essential  Oils"  Vol.   II,   Ed.   II,  1919,  98. 

183  Ann.  157.  236    (1871). 

™Ber.  29.  921  (1896)  ;  SI,  832  (1898). 

195  Roure-Bertrand  Fits'  Bull.  1909,  II,  19. 

166  Ber.  46,  1735  (1913). 

™J.  Chem.  Soc.  103,  1338   (1913). 

168  Harries  &  Haarman.  Ber.  -46,  1737  (1913), 

189  Loc.  cit. 


194      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

geranyl  acetic  acid  was  made,  C10H17 .  CH2CO2H.    Sodium  azide  yields 
the  azoimide  and  corresponding  amine,  geranyl  amine. 

Prileshajev170  has  prepared  the  mono  and  dioxides  of  geraniol  by 
direct  oxidation  by  benzoyl  peroxide.  The  dioxide  is  a  mobile  liquid 
boiling  at  180°-183°  under  25  mm. 

0  0 

CH3     /\  /\ 

>C  —  CH .  CH2CH2C  —  CH .  CH2OH 
CH3  | 

CH3 

geraniol  dioxide    (according  to  Prileshajev) 

Geraniol  is  markedly  less  stable  than  citronellol.  On  heating  with 
phthalic  anhydride  to  200°  geraniol  is  decomposed  but  citronellol  forms 
the  acid  phthalic  ester;  concentrated  formic  acid  also  decomposes  ge- 
raniol much  more  readily  than  citronellol.171  Benzoyl  chloride  at  140°- 
160°  also  decomposes  geraniol,172  but  not  citronellol. 

Isogeraniol:  Evidence  of  a  shift  in  the  position  of  one  double 
bond  in  citral  by  the  action  of  acetic  anhydride  is  furnished  by  the 
isolation  of  an  isomer  of  geraniol  when  the  acetic  ester  of  enol-citral 
is  reduced  by  sodium  amalgam  in  methyl  alcohol  acidified  by  acetic 
acid.173  This  alcohol,  like  geraniol,  has  a  fine  roselike  odor  and  may 
be  distinguished  by  means  of  its  diphenylurethane  melting  at  73°.  Ac- 
cording to  Semmler,  the  formation  of  isogeraniol  may  be  represented 
as  follows: 


CHjOH 


CH3 


170  J.  Russ.  Phys.-Cliem.  Boc.  4%,  613  (1912)  ;  a  trace  of  mineral  acid  hydrolyses 
one  of  the  oxide  groups,  forming  the  glycol,  Ci0H17O.  (OH)3.2H2O  melting-point  94.5°, 
also  the  anhydrous  glycol  CioH17O. (OH)3  in  two  forms  melting  at  145°  and  163°. 

"iWalbaum  &  Stephen,  Ber.  33,  2307  (1900). 

"2Barbier  &  Bouveault,  Compt.  rend.  122,  530   (1896). 

»«  Semmler,  Ber.  kk,  991   (1911). 


ACYCLIC  UNSATURATED  HYDROCARBONS  195 

Linalool:     Linalool  is   isolated  technically   from  oil   of  Central 
American    linaloe   wood.     Its    acetate    is    the   principal    constituent 
of  oil  of  lavender   and  it  is   an  important   component  of   a   great 
number  of  other  essential  oils,  among  which  are  ylang-ylang,  cham- 
paca,  rose,  geranium,  petit-grain,  bergamot,  neroli,  jasmine  and  other 
oils.     It  is  not  easily  isolated  or  purified  since  it  yields  no  crystal- 
line addition  products  or  derivatives  from  which  linalool  can  easily  be 
regenerated.    Hydrogen  chloride  forms  geranyl  chloride,  boiling-point 
82°-86°  at  6  mm.174     Mono  linalyl  phthalate  may  be  prepared  by 
forming  the  sodium  compound  of  linalool,  in  ether  and  allowing  this  to 
stand  several  days  with  phthalic  anhydride.175    Linalool,  being  a  ter- 
tiary alcohol,  is  partially  decomposed  when  acetylation  by  acetic  an- 
hydride is  attempted,  dipentene,  terpinene,  ct-terpinyl  acetate  and  neryl 
acetate  being  formed.176    Continued  heating  with  acetic  anhydride  de- 
composes terpineol,  also  a  tertiary  alcohol,  and  maximum  yields  of  ter- 
pinyl  acetate,  about  85  per  cent,  are  obtained  in  45  minutes.177    When 
diluted  with  xylene,  as  proposed  by  Baulez,  the  maximum  esterifica- 
tion,  about  63  per  cent,  is  obtained  in  7  hours.178    The  conversion  of 
linalool  to  terpinene  and  dipentene  by  heating  with  acids  is  believed  to 
involve  isomerization  to  geraniol. 


Anhydrous  oxalic  acid  is  much  more  energetic  in  its  .action  and  yields 
a  bicyclic  diterpene,  C20H32,  isocamphorene.179 

Oxidation  of  linalool  by  benzoyl  yields  a  mono  oxide  or  dioxide 
depending  upon  the  proportions  of  benzoyl  peroxide  employed  18°  and 


mForster  &  Cardwell,  loc.  cit. 

"'Charabot,  Ann.  chim.  phys.   (7),  21,  232   (1901). 


_  Ber.  S9t  1780   (1906). 

178  Schimmei  &  Co''s  Ber'  im'  I,'  127. 
1™  Semmler,  Ber.  47,  2068    (1914).. 

j^s^^&^s^S&S^S^K^^ 


196      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

H.  Erdmann 181  employed  linalyl  acetate  in  studying  the  addition  of 
sulfur  to  unsaturated  substances  to  form  what  he  terms  thioozonides. 
These  thioozonides  decompose  on  heating,  evolving  hydrogen  sulfide. 

A  tertiary  alcohol  resembling  linalool  and  containing  two  more 
hydrogen  atoms  (one  less  double  bond)  has  been  prepared  by  two  well- 
known  reactions,  which  have  previously  been  discussed  in  connection 
with  the  synthesis  of  hydrocarbons,  and  the  action  of  sulfuric  acid 
upon  olefines.  Thus  dihydromyrcene  on  treating  with  85  per  cent 
sulfuric  acid 182  yields  dihydrolinalool;  the  same  tertiary  alcohol  is 
obtained  by  the  action  of  ethyl  magnesium  bromide  on  methyl  hep- 
tenone. 

(1)  myrcene  ^  CH3  +  H20  ' 

>  C  =  CH .  CH2CH0C  =  CH .  CH3 

CH3  "| 

CH3 

(2)  CH3 

>C  =  CH.CH2CH2G  =  0  +  C2H5MgBr 

H, 


A: 


>         >  C  =  CH .  CH2CH2C  < 

CH3  "|     OH 

CH3 

dihydrolinalool. 

Contrary  to  opinions  previously  held,  Dupont  and  Labaune 183  find 
that  the  double  bonds  in  linalool  and  geraniol  react  with  sodium  sul- 
fite.  These  alcohols  are  completely  dissolved  by  continued  shaking 
with  aqueous  sodium  sulfite,  the  compounds  C10H1S0 .  2NaHS03  hav- 
ing been  isolated.  It  has  long  been  known  that  the  ethylene  bond  in 
citral,  in  the  group  — C  =  CH.CHO  reacts  readily  with  sodium  sul- 

CH8 

fite,  but  this  is  the  first  instance  of  unsaturated  alcohols  reacting  in 
this  manner. 

Citronellol  and  Rhodinol:    From  the  foregoing  discussion  of  these 

adjacent  carbon  atoms.  The  oxide  of  linalyl  acetate,  made  by  Prileshajev's  method, 
reacts  with  water  readily  to  give  the  glycol  Ci0H17(OH)2.O2C2H3  which  on  saponifica- 
tion  yields  Ci0H17(OH)3  melting  at  54°-55°. 

181  Ann.  362,  137    (1908) 

182  Myrcene  is  converted   to   cyclo  dihydromyrcene  by    the   action   of   sulfuric   acid 
in   acetic  acid. 

188  Rmire-Bertrand  FiU>  Bull.  1912,  (3)  6  &  7;  J.  Chem.  Soc.  1913,  I,  746. 


ACYCLIC  UNSATURATED  HYDROCARBONS 


197 


two  substances  it  is  evident  that  these  two  alcohols  occur  together, 
and  while  recognizing  the  probable  existence  of  rhodinol,  the  name 
citronellol  will  be  retained  and,  following  common  usage,  will  be  em- 
ployed for  the  alcohol  C10H200,  containing  one  double  bond,  and  hav- 
ing the  following  physical  properties: 


PHYSICAL  PROPERTIES. 


Observer 
Wallach184 

Tiemann  ** 

Tiemann 18a 

Schimmel  & 
Co.187 

Schimmel  & 
Co.188 

Schimmel  & 
Co. 


Boiling-Point 
1140-115°(12-13mm.) 

117°-118°      (17mm.) 
113°-114°       (15mm.) 


225°-226° 


109° 


225°-226c 


(7mm.) 


Density 

nD 

Method  of 
Isolation 

99° 

0.856^±- 
0.8565-1T 
0.8612^5! 

1.4561 
1.4566 
1.4578 

Destroying 
geraniol  at  250° 

reduction    of 
citronellal 

by  PCI,  method 

0.862 

1.45611 

Wallach's 
method 

j  0.8604 
(  0.8629 

1.4565  ) 
1.4579  f 

From  Java 
citronella 

f  0.862 
1  0.869 

1.459  I 
1.463  | 

Commercial 
preparation  from 
oil  of  geranium 

Citronellol  is  considerably  more  stable  than  geraniol  or  linalool, 
to  the  action  of  alkalies,  10  per  cent  sulfuric  acid,  heating  with  formic 
acid  or  phthalic  anhydride,  phosphorus  trichloride  in  the  cold,  heating 
with  water  as  in  Wallach's  method  of  purifying  citronellol.  The  for- 
mation of  a  cyclic  hydrocarbon  by  loss  of  water  from  citronellol  has 
not  been  observed. 

Citral:  The  constitution  of  citral  and  the  nature  of  citral  a  and 
citral  b  have  been  discussed  in  the  preceding  general  discussion.  The 
following  physical  properties  of  citral  have  been  noted: 


Observer 
Tiemann  &  Semmler"8 

Schimmel  &  Co.190 
Schimmel  &  Co. 


Boiling-Point 


117°-119°(20mm.) 


Density  nD  Source 

0.8972^1     *    1.4931 


0.893*5!          1.4901  lemon- 


92°-  93°  (5mm.)          0.8926  ~L          1.4885          lemon 


1B4Nachr.  K.  Ges.  Wiss.  Gottingen,  1896,  56. 
185  Ber.  29,  906   (1896). 
188  Ibid,  923. 

187  Schimmel  &  Co.'s  Ber.  1898,  62. 

188  Ibid,  1902,  I,  14. 

189  Ber.  26,  2709   (1893). 

190  Schimmel  &  Co.  Rep.  1899,  I,  72. 


198      CHEMISTRY  OF  THE  NON-BENZEN01D  HYDROCARBONS 

In  addition  to  the  chemical  reactions  of  citral  noted  above,  the  fol- 
lowing may  be  noted.  Potassium  acid  sulfate  or  moderately  diluted 
sulfuric  acid  react  on  citral  very  energetically  with  ring  closing,  loss 
of  water  and  the  formation  of  p.cymene. 

The  behavior  of  citral  to  sodium  sulfite  solutions  has  been  the  sub- 
ject of  considerable  investigation.  In  the  presence  of  a  very  slight  ex- 
cess of  free  sulfurous  acid,  in  the  cold,  the  normal,  aldehyde  addition 

OH 

product  C9H15CH<  is  formed,  separating  as  very  fine,  spar- 

OS02Na 

ingly  soluble,  crystalline  plates;  regeneration  of  citral  from  this  de- 
rivative is  not  quantitative.  If  this  crystalline  product  is  allowed  to 
stand,  and  gently  warmed,  with  an  excess  of  bisulfite,  it  goes  into 
solution  as  a  labil  dihydrodisulfonic  acid  derivative,  from  which  citral 
can  be  regenerated  by  the  action  of  caustic  soda,  but  not  by  alkali 
carbonates.  If  the  bisulfite  solution  of  citral  is  strongly  heated,  the 
stabil  dihydrodisulfonic  acid  derivative  is  formed  and  it  is  impossible 
to  regenerate  citral  from  this  stabil  combination.  If  the  labil  dihydro- 
disulfonic acid  salt  is  treated  with  another  molecular  portion  of  citral, 
this  goes  into  solution  as  a  labil  m<mohydrosulfonate  which  can  readily 
be  decomposed  to  citral.  The  formation  of  labil  soluble  sulfonate  of 
citral  can  also  be  carried  out  by  employing  neutral  sodium  sulfite  and 
neutralizing  the  free  alkali,  as  fast  as  formed,  by  acetic  acid.191 

C9H16CHO  +  2Na2S03  +  2H20  ->  C9H15CHO.  (NaHS03)2  +  2NaOH 

This  reaction  usually  gives  so  much  difficulty  that  Tiemann's 192  direc- 
tions may  be  given  here.  A  solution  of  350  g.  sodium  sulfite  in  one  liter 
of  water  is  made  slightly  alkaline  to  phenolphthalein,  treated  with  100 
g.  citral  and  gently  shaken,  keeping  just  slightly  alkaline  by  the  con- 
tinual addition  of  a  calculated  quantity  of  20  per  cent  sulfuric  acid  (or 
acetic  acid) .  The  solution  should  always  be  distinctly  red  by  phenol- 
phthalein, since  in  slightly  acid  solution  the  sparingly  soluble  crystal- 
line compound  will  separate.  The  various  addition  products  formed 
by  sodium  bisulfite  and  citral  may  be  summarized  thus,193  where  X 
represents  the  S03Na  group.  Evidently,  in  the  stable  derivatives,  car- 
bon and  sulfur  are  directly  combined  as  —  C  —  S03Na  or  true  sulfonic 
acid  salts. 

191  Cf.  Gildemeister,  "Die  Aetherischen  Oele,"  Vol.  I.  Ed.  II.  429— (1910). 

™Ber.  31,  3317  (1898). 

188 G.  Romeo,  Qazz.  chim.  Ital.  £8,   (1),  45  (1918). 


ACYCLIC  UNSATURATED  HYDROCARBONS  199 

(1)  normal  aldehyde  addition  product. 

CH3  OH 

>  C  =  CH .  CH2CH2C  =  CH .  CH  <  labil. 
CH3                                                           OS02Na 

CH3 

(2)  stable  dihydrodisulfonate,  formed  in  warm  acid  solutions,  prob- 
ably of  the  type  —  C  —  S03Na. 

CH3      (HX)  (HX) 

>C  —  CH .  CH2CH2C  —  CH .  CHO  stable. 

CH3  I 

CH3 

(3)  labil  dihydrodisulfonate,  formed  in  slightly  alkalins  solutions, 
probably  of  the  type  —  C  —  OS02Na. 

CH3      (HX)  (HX) 

>  C  —  CH .  CH2CH2C  —  CH .  CHO  labil. 
CH3                                   I 

CH3 

(4)  Citral  mono  sodium  hydrosulfonate,  formed  by  citral  +  labil 
citral   dihydrodisulfonate   C9H16CHO.S03Na    (constitution  not 
known) .  labil. 

(5)  Citral  trihydrosulfonate. 

CH3      (HX)  (HX)  OH 

>  C  —  CH .  CH2CH2C  —  CH .  CH  <  labil. 
CH3                                                           OS02Na 

CH3 

(6)  A  stable  form  of  (5).  stable. 

The  hydrogenation  of  citral  is  of  considerable  industrial  interest 
on  account  of  the  availability  of  citral  in  oil  of  lemon  grass  and  the 
possibility  of  its  conversion  into  the  more  valuable  rose  like  citronellol, 
or  the  hydrogenation  of  one  double  bond  only,  yielding  citronellal 
which,  as  noted  above,  is  quantitatively  convertible  into  isopulegol 
and  the  latter  substance  being  convertible  by  hydrogenation  into  the 
well-known  article  of  commerce  menthol,  now  derived  entirely  from  oil 
of  peppermint.  Skita  194  found  that  on  hydrogenating  over  nickel  at 
190°-200°,  chiefly  a  decane  was  formed,  and  at  a  lower  temperature, 
140°,  and  under  pressure  Ipatiev  showed  that  a  decanol  was  the  chief 
product.  Law 195  attempted  to  reduce  citral  by  electrolytic  reduction  in 

m  Chem.  Zentr.  1911,  I,  1209. 

188  J.  Chem.  Soc.  101,  1024   (1912). 


200      CHEMISTRY  OF  THE  NON-BENZEN01D  HYDROCARBONS 

alcohol  acidified  by  sulfuric  acid,  but  he  was  evidently  not  familiar 
with  the  properties  of  citral  and  related  substances  and  it  is  impos- 
sible to  tell  from  his  article  just  what  the  result  was.196  According  to 
Paal  m  hydrogenation  by  colloidal  paladium  or  platinum,  or  by  cat- 
alytic masses  consisting  of  a  supporting  material  on  which  small  pro- 
portions of  one  of  these  metals  are  deposited,  converts  citral  first  to 
inactive  citronellal  and  then  to  the  saturated  aldehyde  tetrahydro- 
citral  ;  geraniol  is  reduced  to  inactive  citronellol  and  the  saturated  alco- 
hol tetrahydrogeraniol.  (This  alcohol  has  recently  been  further  studied 
by  Ishizaka,  Ber.  41,  2483  (1914)  ,  who  also  prepared  it  by  PaaFs  meth- 
od.) Skita  states  that  citral  yields  both  citronellal  and  citronellol  to- 
gether with  a  dimolecular  aldehyde  C20H3402  when  using  colloidal 
palladium  as  a  catalyst. 

Condensation  of  aliphatic  aldehydes  with  (3-naphthylamine  and 
pyruvic  acid  usually  yields  well  crystalline  products  suitable  for  the 
purpose  of  identification.  Citral  condenses  with  these  two  substances 
to  form  citryl-p-naphthocinchoninic  acid,  melting  at  199°-200°.  Cit- 
ral oxime  and  the  phenylhydrazone  are  liquid  at  ordinary  tempera- 
tures. Cyanacetic  and  malonic  acid  condense  readily  yielding  well 
crystalline  products. 

CN  CN 

C9H15CHO  +  H2C  <  --  >  C9H15CH  =  C  < 

C02H  C02H 

C02H.  C02H 

C9H15CHO  +  H2C<  --  >  C9H15CH  =  C< 

C02H  C02H 

Citral  also  condenses  readily  with  acetone  in  the  presence  of  alka- 
lies, and  this  led  Tiemann  198  to  the  discovery  of  the  ionones.  The  for- 
mation of  psewdo-ionone  is  an  example  of  the  well-known  type  of  con- 
densation illustrated  by  the  formation  of  croton  aldehyde,  and  mesityl 
oxide.  According  to  Tiemann's  patent  specifications  the  condensation 
is  effected  by  means  of  barium  hydroxide,  but  other  condensing  agents 
give  better  results,  for  example  5  per  cent  of  sodium  ethoxide  in  abso- 
lute alcohol.199  The  resulting  mixture  is  distilled  and  the  fraction 
boiling  at  138°-155°  at  12  mm.  is  purified  from  unchanged  citral  and 
condensation  products  formed  from  acetone  alone,  by  distilling  with 

19*I^t^ie  °PIRion  of  tfle  writer,  Law's  experiments  are  of  considerable  interest 
and  would  be_  worth  repeating  with  the  cooperation  of  a  skilled  organic  chemist. 

ohem-  4t«-  8-  1019 


"•Slack,  Pref.  &  Eaa.  Oil  Record.  7,  389   (1916). 


ACYCLIC  UNSATURATED  HYDROCARBONS 


201 


steam,  these  impurities  being  easily  volatile.  By  a  second  vacuum  dis- 
tillation of  this  product  a  very  pure  pseudo-ionone  boiling  at  143°-145° 
is  obtained. 


CH2 
CH3 
CH3 


>  C  =  CH .  CH2CH2C  =  CH .  CHO  +  H3C  —  CO  —  CH, 


CH3 


>C  =  CH.CH2CH2C  =  CH.CH  =  CH.COCH3 
AH. 

pseudo-ionone. 

The  physical  properties  of  pseudo-ionone  are  as  follows;  specific 
gravity  at  20°  =  0.8980,  refractive  index-p  =  1.53346,  boiling-point 
at  12  mm.  —  143°-145° 

When  pseudo-ionone  is  heated  with  dilute  sulfuric  acid,  about  1 
per  cent,  for  several  hours,  ring  closing  results,  probably  through  the 
intermediate  addition  of  water  and  subsequent  decomposition,  giving 
two  isomeric  ionones,  designated  as.  a  and  (3. 


— CH- 


,H 


CH,      CH 


oc-ionone 


VH=CHCO 

CH, 


r— CH. 


CH, 


/3-ionone 


The  odors  of  the  two  isomers  are  noticeably  different,  a-ionone 
having  a  sweeter  odor  more  nearly  resembling  orris  root  and  p-ionone, 
in  very  dilute  solutions,  about  1  :  10,000,  resemblirig  more  closely  the 
fresh  wood  violet.  Commercial  ionone  is  usually  a  mixture  of  the 
two  isomers  containing  mostly  a-ionone.  The  conditions  under  which 
pseudo-ionone  is  condensed  affect  the  relative  proportions  of  a  and 
p-isomers,  more  concentrated  sulfuric  acid  at  low  temperatures  in- 
creasing the  proportion  of  p-ionone  while  phosphoric,  hydrobromic  and 
hydrochloric  acid  yield  chiefly  a-ionone.  Many  methods  have  been 
proposed  to  separate  the  two  isomers,  of  which  two  only  will  be  men- 
tioned. Pure  a-ionone  was  isolated  by  Tiemann  by  making  the  oxime 


202      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


of  a  commercial  ionone  containing  mostly  a-ionone,  recrystallizing  the 
oxime  from  petroleum  ether  and  regenerating  the  ketone  by  means  of 
dilute  sulfuric  acid.  One  method  of  separation  is  based  upon  the  in- 
solubility of  the  sodium  hydrosulfonate  of  a-ionone  in  aqueous  sodium 
chloride  solutions.200  If  sodium  chloride  is  added  to  a  hot  solution  of 
the  sodium  hydrosulfonates,  the  a-ionone  derivative  separates,  crystal- 
lizing in  very  small  plates;  the  (3-ionone  hydrosulfonate  remains  in  so- 
lution. Gildemeister 201  notes  the  following  physical  properties  for 
commercial  ionone;  boiling-point  104°-109°  (4  to  5  mm.),  d150  0.9350 

20° 
to  0.9403,  n  jj-  1.5033  to  1.5051.    Chuit202  gives  the  following  for  the 

two  isomers. 

a-Ionone  P-Ionone 

Boiling-point    127.6°(12mm.)  134.6° (12mm.) 

Density,  15°  0.9338  0.9488 

Refractive  index  1.50001  1.52008 

p-Bromophenylhydrazone,  M.  P 142°-143°  116°-118° 

Semicarbazone    107M080  148°-149° 

The  ionones  may  be  hydrogenated  to  the  ketone  tetrahydroionone 
by  means  of  hydrogen  and  colloidal  palladium  203  or  the  ketone  group 
may  be  converted  to  >CH2  without  affecting  the  double  bonds.204 

Irone:  On  account  of  its  similarity  to  the  ionones,  this  ketone,  an 
isomer  of  the  synthetic  violet  ketones,  may  be  mentioned  here.  It  was 
isolated  from  the  volatile  oil  of  orris  root  and  studied  by  Tiemann.  It 
has  been  made  by  the  condensation  of  A4  cyclocitral  and  acetone,205 
and  its  close  similarity  to  the  ionones  is  shown  by  the  following  struc- 
ture. 


H.CH, 


H.CH=CHCO 

CH3 
CH3      NCH3 

The  physical  properties  of  irone  are,  boiling-point  144°   (16  mm), 

20° 
d150  0.9391,  n  -=y  1.5017.    Its  characteristic  derivatives  are  the  oxime, 


200  Chuit,  Rev.  Gen.  Chim.  6,  432   (1903). 

n"Die  Aetherischen  Oele",  Vol.  I,  485.  Ed.  II   (1910). 
202  Loc.  cit. 
z03Skita,  Ber.  45,  3312   (1912). 

04Kishner,  J.  Russ.  Phys.-Chem.  Soc.  tf,  1398   (1912). 
2MMerhng  &  Welde,  Ann.  366,  119   (1909). 


ACYCLIC  UNSATURATED  HYDROCARBONS 


203 


melting  point  121.5°,  p-bromophenylhydrazone  melting  at  174°-175° 
and  thiosemicarbazone  melting  at  181°.  Irone  is  not  made  syntheti- 
cally on  an  industrial  scale,  nor  isolated  as  such  from  the  volatile  oil 
of  violet  root,  or  orris. 

In  view  of  the  commercial  value  of  the  ionones  Merling  and 
Welde206  undertook  a  study  of  similarly  constituted  unsaturated 
ketones.  Any  slight  change  in  the  constitution  of  these  ke- 
tones  causes  considerable  difference  in  odor.  While  the  group 
-  CH  =  CH  —  CO  —  CH3  is  essential  to  odors  of  this  kind,  as  is 
shown  by  the  fact  that  on  hydrogenating  the  double  bonds,  the  fra- 
grance of  the  ionones  disappears,  the  particular  quality  of  the  odor  is 
influenced  greatly  by  the  relative  positions  of  the  other  ethylene  bond 
and  the  methyl  groups.  Condensation  products  with  acetone  were  pre- 
pared from  the  following  three  aldehydes,  isomeric  with  cyclocitral. 


HO 


CHO 


The  product  derived  from  I  was  almost  odorless  but  the  products 
from  II  and  III  had  faint  violet  like  odors.  The  most  intense  odor  is 
obtained  when  the  aldehyde  group  is  situated  between  the  methyl  and 
dimethyl  groups.  The  perfume  character  of  such  acetone  conden- 
sation products  disappears  when  the  aldehyde  group  does  not  adjoin 

CH3 

a  methyl  group.    Nevertheless  the  grouping  — C  — CH —  C<  does 

CH3  CHO   CH3 

not  yield  a  perfume  when  condensed  with  acetone,  as  is  shown  by  the 
condensation  product  obtained  from  (3-isopropylbutaldehyde  and  ace- 
tone, but  when  these  groups  are  present  in  the  cyclogeraniolene  ring, 
a  perfume  results.  The  importance  of  the  tertiary  butyl  group 
—  C(CH3)3,  to  the  odor  of  musk,  has  been  brought  out  by  the  work 

206  Ann.  366,  119  (1909). 


204      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

of  Bauer  on  artificial  musk.207    Austerweil 208  has  shown  that  the  group 
=  CH.CRR1  appears  to  be  necessary  to  produce  geraniol  like 


odors. 

The  condensation  of  citral  with  ethyl  acetoacetate  has  been  studied 
by  Knoevenagel 209  who  isolated  five  isomeric  ethylcitrylidene  acetol 
acetates.  Condensation  is  brought  about  by  adding  a  very  small  quan- 
tity of  piperidine  to  a  mixture  of  ethyl  acetoacetate  and  citral  at 
—  15°  and  allowing  to  stand  two  days.  The  structure  of  these  con- 
densation products  is  not  yet  definitely  known. 

Citral  reacts  normally  with  methyl  or  ethyl-magnesium  bromide 
to  give  secondary  alcohols  of  rose  like  odor.210 

Sesquicitronellene,  C15H24.  This  so-called  aliphatic  sesquiterpene 
was  discovered  in  Java  citronella  oil  by  Semmler  and  Spornitz.211  It 
has  four  double  bonds,  three  of  which  are  probably  conjugated. 

Mol.  Ref.  74.53 

Mol.  Ref.  calc.  for  C15H24  /=  4  69.6 


E  M—  4.9 

Sodium  and  alcohol  readily  reduce  it  to  C15H26  (evidence  of  at  least 
one  pair  of  conjugated  double  bonds)  and  hydrogen  in  the  presence  of 
platinum  black  yields  the  saturated  acyclic  hydrocarbon  C15H32.  As 
is  frequently  observed  among  the  sesquiterpenes  ring  closing  is  easily 
effected,  being  brought  about  in  this  case  by  concentrated  formic  acid. 
Sodium  and  alcohol  do  not  reduce  the  cyclic  hydrocarbon  showing 
that  ring  formation  has  occurred  through  one  of  the  conjugated  double 
bonds.  The  original  Sesquicitronellene  is  readily  oxidized  and  poly- 
merized. Its  physical  properties  are,  boiling-point  138°-140°  (9  mm.) , 
d20  0.8489,  nD  1.53252. 

Spinacene.  C30H60.  This  very  remarkable  unsaturated  hydrocar- 
bon has  recently  been  described  by  Chapman212  and  by  Tsujimoto.218 
It  has  been  found  in  the  livers  of  several  species  of  the  Spinacidae,  a 
family  of  the  Selachoidei,  or  sharks,  and  Chapman  has  therefore  named 
it  spinacene.  In  the  fresh  liver  oils  of  certain  species  this  hydrocarbon 

•"  Ber.  £4,  2832  (1891)  ;  32,  3647  (1899). 
108  Compt.  rend.  151,  440  (1910) 


.          .       ,  . 

*»J.  prakt.  chem.   (2),  97,  288   (1918). 
810  Bayer  &  Co.,  Chem.  Zentr.  1904,  II,  624,  1269. 
™Ber.  46,  4025   (1913). 

*a  J.  Chem.  8oc.  Ill,  56   (1917)  ;  113,  458   (1918), 
™Chem.  Aba,  n,  1004  (1918). 


ACYCLIC  UNSATURATED  HYDROCARBONS  205 

constitutes  about  90  per  cent  of  the  oil.  Fish  liver  oils  previously 
known,  such  as  those  of  the  haddock,  skate,  hake,  cod,  and  tunny, 
contain  only  about  2  per  cent  of  unsaponifiable  matter  which  appears 
to  be  cholesterol.  From  the  standpoint  of  physiological  chemistry, 
the  manner  of  formation,  secretion  and  physiological  utilization  of  such 
an  oil  is  of  great  interest,  and  inasmuch  as  the  sharks  are  found,  fos- 
silized, in  many  strata,  geologically  very  old,  the  probability  that 
shark  liver  oils  have  contributed  to  the  formation  of  petroleum  is  at 
once  suggested. 

Chemically,  spinacene  is  of  more  than  ordinary  interest.  Dry  hy- 
drogen chloride  passed  into  a  cooled  ether  solution  of  spinacene  forms 
the  crystalline  hexahydrochloride,  C30H50.6HC1,  and  bromine  in  dry 
ether  yields  the  crystalline  dodecabromide  C30H50Br12.  Like  chlorine 
and  bromine  derivatives  of  petroleum  hydrocarbons  and  the  terptnes, 
these  spinacene  derivatives  are  unstable  and  readily  decompose  on  heat- 
ing. The  hydrocarbon  accordingly  contains  six  double  bonds.  A  moder- 
ately stable  crystalline  trinitrosochloride  can  be  prepared  by  the  usual 
methods.  By  catalytic  hydrogenaton  by  means  of  platinum  black,  Chap- 
man obtained  the  saturated  hydrocarbon  C30H62,  which  is  liquid  at 
—  20°  and  therefore  is  not  a  normal  paraffine.  Exaltation  of  the  re- 
fractive index  and  partial  polymerization  by  metallic  sodium  indicate 
that  probably  two  pairs  of  double  bonds  are  in  conjugated  positions. 
On  distilling  over  sodium,  partial  decomposition  also  occurs,  forming  a 
hydrocarbon  C10H18,  which  appears  to  be  a  monocyclic  hydrocarbon 
containing  one  double  bond,  boiling  at  170°-175°,  and  much  resem- 
bling cyclodihydromyrcene  in  its  properties. 

Cholesterylene:  The  hydrocarbons  resulting  from  the  decomposi- 
tion of  cholesterol  or  cholesteryl  chloride  have  been  repeatedly  in- 
vestigated on  account  of  the  possible  connection  of  this  hydrocarbon 
with  the  optical  activity  of  petroleum.  The  properties  of  "choles- 
terylene" vary  considerably  according  to  its  method  of  preparation. 
When  equal  parts  of  cholesterol  and  infusorial  earth  are  rapidly  heated 
to  280°-300°  a  solid  cholesterylene  is  obtained,  which  is  capable  of 
adding  four  atoms  of  hydrogen  to  form  the  solid  cholestane.  A  sim- 
ilar mixture  slowly  heated  for  about  eight  hours  at  300°  gives  an  oil, 
probably  a  mixture,  boiling  at  257°-267°  at  12  mm.,  D  =  0.9572  and 
[a]  D  +  49.12°.  The  product  obtained  by  rapid  heating  is  laevo  ro- 
tatory.214 Cholesteryl  chloride  215  yields  an  oil  having  properties  prac- 
tically identical  with  those  noted  above. 

»*Steinkopf,  J.  prakt.  chem.   (2)  100,  65   (1919). 

«"  Mauthuer  &  Suida,  J.  Chem.  800.  Aba.  1904,  I,  49 ;  1909,  I,  714. 


206      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


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I  1 

i-(  O5 


a  a       a 
a  a       a 

O      »0  10 


C^     t"      to 

l-H        Cq        l-l 


ACYCLIC  UNSATURATED  HYDROCARBONS        209 

1  v.  Braun,  Ann.  382,  22  (1911);  Zelinsky  and  Prshevalsky,  J.  Russ  Phys  - 
Chem.  Soc.  89,  1,  1168  (1907). 

2  Brooks  and  Humphrey,  J.  Am.  Chem.  Soc.  40,  833  (1918). 

3  Jawein,  Ann.  195,  255;  Ipatiev,  Chem.  Zentr.  1899,  II,  177. 

4  Umnova,  J.  Russ.  Phys.-Chem.  Soc.  42,  1530  (1911). 

5  Wislicenus,  Ann.  219,  313;  Jawein,  Ann.  195,  255  (1879). 

6  Fomin  and  Sochanski,  Ber.  46,  244  (1913). 

7  Delacre,  Chem.  Zentr.  1906  (1),  1233. 

8  Henry,  Compt.  rend.  144,  553  (1907). 

9  Kondakow,  J.  prakt.  Chem.  (2),  62,  174  (1900). 

10  Welt,  Ber.  30,  1495;  Przewalski,  Chem.  Zentr.  1909  (2),  794. 

11  Sabatier  and  Senderens,  Compt.  rend.  135,  88  (1902). 

12  Schorlemmer  and  Thorpe,  Ann.  217,  150  (1902). 

13  Bjelouss,  Ber.  45,  625  (1912). 

14  Sayzew,  /.  prakt.  Chem.  (2)  57,  38  (1898). 

15  Kaschirsky,  Ber.  11,  985  (1878). 

16  Pawlow,  Ann.  173,  194  (1874). 

17  Butlerow,  /.  Russ.  Phys.-Chem.  Soc.  7,  44  (1875). 

18  Senderens,  Compt.  rend.  144,  1110. 

19  Briihl,  Ann.  235,  11;  Eijkwan,  Chem.  Zentr.  1907  (2),  1210. 

20  Muset,  Chem.  Zentr.  1907  (1),  1313. 

21  Sokolow,  J.  prakt.  Chem.  (2),  39,  444  (1889) ;  Clarke  and  Riegel,  /.  Am. 
Chem.  Soc.  34,  679  (1912). 

22  Grigorowitsch  and  Pawlow,  /.  Russ.  Phys.-Chem.  Soc.  23,  172  (1891). 

23  Mannich,  Ber.  35,  2145  (1902). 

24  Freund,  Ber.  24,  3359  (1891). 

25  Bjelouss,  Ber.  45,  625  (1912). 

26  Grosjean,  Ber.  25,  478  (1892). 

27  Kishner,  Chem.  Zentr.  1900,  II,  725. 

28  Wallach,  Ann.  408,  163  (1915). 

29  Kishner,  J.  Russ.  Phys.-Chem.  Soc.  43,  951  (1911). 

30  Wolff,  Ann.  394,  86  (1912). 

31  Bjelouss,  Ber.  45,  625  (1912). 

32  Grignard,  Bull.  Soc.  chim.  (3),  31,  753. 

33  Kondakow,  J.  Russ.  Phys.-Chem.  Soc.  28,  808  (1896). 

34  Thorns  and  Mannich,  Ber.  36,  2546  (1903). 

35  Ross  and  Leather,  Chem.  Zentr.  1906  (2),  1294. 

36  Bjelouss,  Ber.  45,  625  (1912). 

37  Krafft,  Ber.  16,  3020  (1883). 

38  Grignard,  Chem.  Zentr.  1901  (2),  624. 

39  Freylon,  Ann.  chim.  20,  58  (1910). 

40  Klages,  Ber.  36,  3586  (1903). 


Chapter  VI.     Polymerization  of 
Hydrocarbons. 

The  polymerization  of  unsaturated  hydrocarbons  is  a  phenomenon 
the  mechanism  of  which  is  exceedingly  obscure,  in  fact,  no  very  plaus- 
ible theories  have  been  advanced  to  explain  this  kind  of  condensation, 
although  the  process  is  accepted  and  utilized  daily  in  the  industries. 
When  unsaturated  petroleum  hydrocarbons  are  polymerized  by  sul- 
furic  acid  it  has  been  assumed  that  alkyl  sulfuric  acid  esters  are 
formed  which  may  then  condense  with  other  molecules  of  the  original 
olefine,  with  the  liberation  of  sulfuric  acid,1 

(1) 


However,  polymerization  of  hydrocarbons  is  brought  about  by  a  great 
variety  of  substances,  energetic  reagents  such  as  anhydrous  aluminum 
chloride  or  bromide,  zinc  chloride,  ferric  chloride,  sulfur  chloride,  and 
also  such  substances  as  fuller's  earth,  forms  of  energy  such  as  light, 
heat,  the  silent  electric  discharge  and  also  certain  metals,  for  example, 
metallic  sodium.  It  is  quite  probable,  therefore,  that  we  shall  have  to 
go  much  deeper  than  the  drawing  of  graphic  formulae  for  plausible 
theories  of  polymerization;  in  fact,  the  question  really  is  one  involv- 
ing the  nature  of  valence.  It  is  beyond  the  scope  and  purpose  of  the 
present  volume  to  go  far  afield  in  reviewing  the  subject  of  valence, 
but  there  are  a  number  of  phenomena,  such  as  polymerization  and  the 
mechanism  of  organic  reactions,  absorption  of  light  and  its  alteration 
as  in  fluorescence,  and  the  decomposition  of  substances  under  the  in- 
fluence of  heat  which  are  undoubtedly  very  closely  related  and,  with 

1Kondakow,  J.  prakt.  cKem.  5k,  442   (1896). 

210 


POLYMERIZATION  OF  HYDROCARBONS  211 

valence,  belong  fundamentally  to  the  subject  of  the  constitution  of 
matter.  The  observations  noted  in  the  following  discussion  have  been 
brought  together  on  account  of  their  interest  to  organic  chemists,  rather 
than  for  any  light  that  may  be  thrown  upon  the  mechanism  of  poly- 
merization. 

Ethylene,  as  noted  elsewhere  in  these  pages,  is  relatively  stable,  but, 
at  temperatures  within  the  range  400°-450°,  condensation,  in  contact 
with  iron  or  copper,  is  fairly  rapid.2  Many  substituted  ethylenes  con- 
taining negative  groups  such  as  chlorine,  or  the  phenyl  group,  poly- 
merize on  standing  at  room  temperature,  for  example,  styrene 
C6H5CH  =  CH2,  vinyl  chloride  CH2  =  CHC1  (polymerization  is  par- 
ticularly rapid  in  sunlight),  1, 1-dichloroethylene  CH2  =  C.C12,  vinyl 
bromide  in  sunlight,  1-chloro-l-bromoethylene  CH2  =  C.ClBr,  and 
1,  1-dibromoethylene  CH2  =  CBr2.  These  substances  are  rapidly  oxi- 
dized by  air  or  oxygen.  On  the  other  hand,  allyl  chloride  and  bromide, 
CH2  =  CH.CH2X,  trichloroethylene  CHC1  =  CC12,  and  1.2  dibromo- 
ethylene,  CHBr  =  CHBr  are  not  spontaneously  polymerized  and  are 
not  appreciably  oxidized  on  standing  in  contact  with  air  or  oxygen. 

Vinyl  bromide,  CH2  =  CHBr,  is  polymerized  on  standing  in  sun- 
light to  what  Ostromuislenski 3  calls  a-caouprene  bromide.  Polymeri- 
zation under  these  conditions  is  very  greatly  affected  by  other  sub- 
stances, light  low  boiling  hydrocarbons  very  greatly  retarding  the  re- 
action. This  polymer,  a-caouprene  bromide,  dissolves  very  readily 
in  carbon  bisulfide  and  its  chemical  properties  are  of  particular  inter- 
est, for  example,  it  is  quite  inert  to  inergetic  oxidizing  agents  and  to 
concentrated  mineral  acids.  Under  the  influence  of  ultraviolet  light 
the  polymerization  appears  to  proceed  further,  forming  what  have  been 
named  P-  and  y-caouprene  bromides.  The  (3-caouprene  bromide  is  solu- 
ble in  carbon  bisulfide  but  the  y-product  is  quite  insoluble  but  swells 
in  this  solvent.  The  y-product  may  be  converted  into  the  soluble 
(3-bromide  by  boiling  with  chlorobenzene  and  then  precipitating  with 
petroleum  ether.  The  tetrabromide  of  butadiene-caoutchouc,  de- 
scribed by  Harries,  also  exists  in  three  forms  whose  behavior  is  ap- 
parently identical  with  the  polymerized  vinyl  bromides  just  de- 
scribed. Ostromuislenski  regards  the  polymers  of  vinyl  bromide  as 
structurally  arranged  as  follows, 

.  CH9CHBr.CH2CHBr.CH2CHBr  . 


>  Ipatiev,  J.  Chem.  Soc.  A 6s.  1907,  I,  5. 
•  J.  Rust.  Phys.-Chem.  Soc.  44,  204  (1912). 


212      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

Butylene,  amylenes  and  hexylenes  are  more  easily  polymerized 
than  their  higher  homologues  and  when  condensation  of  such  mono- 
olefines  occurs,  ring  formation  does  not  take  place. 

Hydrocarbons  containing  two  or  more  conjugated  ethylene  bonds 
are  more  rapidly  oxidized  by  oxygen  and  are  very  easily  polymerized, 
as,  for  example,  butadiene  (also  called  erythrene  and  divinyl)  isoprene, 
dimethylallene,  piperylene,  the  so-called  aliphatic  terpenes,  myrcene 
ocimene,  cyclopentadiene  and  the  fulvenes,  cyclohexadiene  and  the  like. 
The  structure  of  the  polymers  of  these  substances  is  known  in  but  few 
instances,  but  one  instance  of  ring  formation  is  well  known,  i.  e.,  the 
condensation  of  isoprene  to  the  cyclohexene  derivative  dipentene.  Also, 
dimethyl  and  tetramethylallene  yield  cyclobutane  derivatives  on  poly- 
merization. 

Dimethylallene,  (CH3)2C  =  C  =  CH2,  is  of  iterest  as  an  isomer  of 
isoprene.  This  hydrocarbon  may  readily  be  converted  to  isopropyl 
acetylene,  and  vice  versa,  indicating  that  the  internal  stress  in  the  two 
hydrocarbons  is  approximately  of  the  same  order, 

(CH3)  2C  =  C  =  CH2  ±5  (CH8)  2CH  —  C  =  CH. 

Tetramethylallene  is  also  easily  changed  to  an  acetylene  derivative. 
In  the  series  beginning  with  allene  and  including  methyl,  dimethyl,  tri- 
methyl  and  tetramethylallene,  the  stability  diminishes  with  increasing 
substitution  of  methyl  groups.4 

When  dimethylallene  condenses  to  the  dimeric  cyclobutane  deriva- 
tive six  isomeric  hydrocarbons  are  possible  but  two  have  been  iso- 
lated, i.  e., 

CH2  —  C  =  C(CH3)2  boiling-point  61°-62°,  9  mm. 
CH2  —  C  =  C(CH3)2 

CH2  =  C  —  C(CH3)2  boiling-point  37°-38°,  9  mm. 
(CH3)2C  — C  =  CH2 
Tetramethylallene  condenses  to  the  hydrocarbon.5 

*  Mereshkowski,  J.  Russ.  Phya.-chem.  Soc.  tf,  1940  (1913).  Tetramethylallene  was 
obtained  pure  for  the  first  time  by  Mereshkowski,  by  treating  (CH3)2C=C — CH(CH8)a 

Br 

with  alcoholic  caustic  potash  in  an  autoclave  at  130°,  illustrating  the  marked  effect 
of  the  double  bond  on  the  reactivity  of  the  bromine  atom. 

8  This  hydrocarbon  has  the  unusually  high  optical  exaltation  of  2.596,  due  doubt- 
less to  conjugated  linkings  of  semi-cycUc  character  and  also  perhaps  to  the  presence 
of  the  cyclobutane  ring. 


POLYMERIZATION  OF  HYDROCARBONS  213 


- 
)2C  —  C  = 


(CH3)2C-C  =  C(CH3)2 

Polymerization  is  a  property  which  is  probably  common  to  all  sub- 
stances containing  ethylene  linkings.6 

In  a  study  of  the  polymerization  of  a,  (5  unsaturated  ketones,  Ru- 
zicka  [Helv.  chim.  Acta,  8,  781  (1920)  ]  showed  that  the  point  of  at- 
tack was  the  ethylene  bonds,  not  the  CO  groups. 

Conjugated  Dienes  and  the  Synthesis  of  Rubber. 

The  preparation  of  conjugated  dienes  has  become  a  matter  of  great 
interest  on  account  of  the  property,  which  some  of  these  unsaturated 
hydrocarbons  possess  of  polymerizing  to  rubber-like  substances.  Many 
industrially  important  organic  substances  derived  from  natural  sources 
can  also  be  manufactured  by  synthetic  methods  but  the  competition 

•Ethylene  bonds  undoubtedly  play  a  very  essential  part  in  the  polymerization  of 
fatty  oils,  and  the  phenomenon  is  most  pronounced  in  the  case  of  highly  unsaturated 
oils  such  as  tung,  linseed,  walnut  and  certain  fish  oils.  However,  the  glycerine  and 
carboxyl  groups  also  probably  enter  into  the  process  of  condensation.  Kronstein 
(Ber.  49,  722  [1916]  showed  that  olive  and  cottonseed  oils  contain  considerable  pro- 
portions of  glycerides  which  gelatinize  like  tung  oil  if  the  non-polymerizing  portions 
of  these  oils  are  first  removed  by  distillation.  Polymerization  of  these  oils  is  accom- 
panied by  a  decrease  in  their  iodine  absorption  values.  Depolymerization  takes  place 
readily  since  Morell  (J.  Soc.  Ctiem.  Ind.  57,  181  [1918])  has  shown  that  the  methyl 
esters,  derived  from  polymerized  tung  oil,  are  of  normal  molecular  weight.  Salway 
(J.  Soc.  Ch&m.  Ind.  89,  324T,  [1920])  shows  that  the  introduction  of  free  fatty  acids 
accelerates  the  polymerization  of  such  oils  (whale  oil),  and  when  the  free  fatty  acids 
are  heated,  decrease  of  the  iodine  value  and  refractive  index  occurs.  When  the  natural 
glycerides  are  heated,  Salway  supposes,  (1)  splitting  off  of  free  fatty  acid  ;  (2)  con- 
densation of  the  free  fatty  acid  with  the  unsaturated  linkings  of  the  fatty  oil;  (3) 
possible  anhydride  formation  in  which  reaction  the  free  alcoholic  glyceryl  radicles  take 
part. 

(1) 

CH2O.OCR  CH2OH. 

CH2O.OCR  -^  CH2O.OCR.      +      RCO.OH. 

CH2O.OC  (CH2)  4CH=CH.C11H19  CH.O.OC  (CH2)  4CH=< 

(2) 

CH2OH.  CH2 — 0 — CH2 

-^CH2O.OCR  C....  C.... 

CH2O.OC.  (CH2)  4CH— CHj.AiHw  C . . . .  C . . . . 

anhydride 
LOCR  formation 


214       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

* 

of  the  two  methods  is  often  very  close,  and  while  the  future  of  syn- 
thetic rubber  is  a  matter  of  opinion,  all  chemists  interested  in  this 
problem  should  keep  in  mind  the  fact  that  plantation  rubber  from 
Hevea  braziliensis  can  be  produced  at  a  cost  of  approximately  twenty- 
five  cents  per  pound.  The  present  relative  importance  of  synthetic 
and  natural  rubber  is  not  a  matter  of  opinion,  but  of  record,  and  with 
the  exception  of  a  quantity  produced  in  Germany  during  the  war,  no 
synthetic  rubber  has  been  produced  on  an  industrial  scale  or  at  prices 
which  threaten  the  rubber  plantations.  The  production  of  rubber  from 
Hevea  plantations  has  been  much  greater  than  the  pioneers  of  the  in- 
dustry had  anticipated  on  account  of  the  "wound  response"  of  the  trees 
on  tapping.7  The  synthesis  of  good  gutta  percha  would  seem  to  offer 
a  better  chance  of  commercial  success  on  account  of  the  slow  growth 
of  the  trees  yielding  gutta  and  the  apparent  difficulties  of  solving  this 
phase  of  the  rubber  business  by  plantation  methods.  Yet  even  in  this 
case  the  struggle  between  synthetic  and  natural  camphor  is  suggestive. 
Camphor  trees  are  seldom  felled  for  camphor  distillation  until  they 
have  reached  the  age  of  approximately  fifty  years,  yet  camphor  plan- 
tations, distilling  the  leaves  and  twigs,  have  been  undertaken  on  an  ex- 
tensive scale  and  the  cost  of  manufacturing  synthetic  camphor  has 
increased  with  the  higher  cost  and  diminishing  supply  of  turpentine, 
the  necessary  raw  material. 

The  history  of  the  subject8  of  artificial  rubber  has  been  marred 
by  polemical  controversies  which  have  arisen  largely  on  account  of 
definitions  and  the  difficulty  of  determining  just  what  rubber  is  struc- 
turally and  the  difficulty  of  proving  the  identity  of  such  amorphous 
substances.  As  regards  the  question  of  the  identity  of  polymerized  iso- 
prene  rubber  and  natural  Hevea  rubber,  it  now  appears  that  the  former, 
when  made  either  by  polymerization  by  metallic  sodium  or  by  per- 
oxides, is  not  homogenous,  as  is  indicated  by  the  fact  that  the  ozonides 
yield  succinic  acid,  acetonylacetone,  laevulinic  aldehyde  and  laevulinic 
acid,  corresponding  to  the  two  dimeric  isoprene  complexes  1.5-di- 
methyl-A^-cyclo-octadiene  and  1  .G-dimethyl-A^-cyclo-octadiene.9 
Natural  Hevea  rubber,  on  the  other  hand,  appears  to  be  a  homogenous 
product,  the  ozonide  decomposition  products  being  referrable  to  the 


»i  ^ubber  Cultivation  in  the  Far  East,  Science  Progress.  I.  Jan.  1910  ;  II. 

April,  1910.  According  to  Eaton,  Chem.  Trade  J.  1921,  242  approximately  2,000,000 
acres  are  under  cultivation  for  rubber. 

,in-.flFf-T,Po,n.d'  J'  Am"  Chem-  ®oc-  36,  165  (1914)  ;  Luff,  J.  Soc.  Chem.  Ind.  85,  983 
ilo  oU  PSSP"k.liJS?0>  uh€m-  Ind-  S1>  616  (1912)  ;  Gottlob,  Indiana,  Rubber  J.  58,  305, 
o4o,  oyl,  4oo  (1919). 

•Steimmig,  Ber.  47,  350  (1914). 


POLYMERIZATION  OF  HYDROCARBONS  215 

1.5-dimethyl-A1-5-cyclo-octadiene  complex.  The  first  direct  evidence 
obtained  by  Harries  of  an  eight  carbon  ring  complex  was  later  shown 
to  be  incorrect,  the  ketone  then  considered  to  be  cyclo-octane-1 .5-dione 
proving  to  be  impure  heptane-2 . 6-dione.10  For  practical  purposes, 
however,  Ostromuislenski  is  little  concerned  with  chemical  standards 
of  comparison  between  natural  rubber  and  synthetic  colloids  resembling 
them,  and  advocates X1  a  classification  based  upon  the  temperatures  at 
which  the  colloid  acquires  and  loses  its  elastic  properties,  and  the 
range  between  these  temperature  limits.  When  these  agree  closely 
with  the  values  for  natural  caoutchouc  he  proposes  that  the  colloid  be 
classed  as  normal,  regardless  of  its  ozonide  decomposition  products. 
Considering  the  conflicting  results  of  different  experimenters  with  the 
ozone  method,  and  the  difficulties  of  such  work,  the  proposed  classifi- 
cation would  probably  be  as  consistent  and  also  more  useful. 

Harries  has  contended  that  the  earlier  investigators,  who  discov- 
ered the  polymerization  of  isoprene,  did  not  really  produce  caoutchouc, 
but  the  question  seems  a  futile  and  purposeless  one.  That  isoprene 
could  be  polymerized  to  an  amorphous  rubber-like  substance  was  evi- 
dent from  the  early  work  of  Greville  Williams 12  who  did  not  recog- 
nize his  product  as  rubber,  but  whose  description  of  the  product,  to- 
gether with  the  results  of  later  repetition  of  his  work,  indicate  that  his 
product  was  in  fact  rubber,  and  Bouchardat13  who,  in  1875,  treated 
isoprene  with  concentrated  hydrochloric  acid  at  0°,  and  Tilden14 
who  obtained  a  similar  product  in  1882  and  announced  later,  1892,  that 
isoprene  polymerizes  spontaneously  on  long  standing  in  the  light  and  in 
contact  with  air.15  Wallach  16  showed  that  light  causes  the  polymeri- 
zation of  isoprene  in  a  sealed  tube,  but  the  change  is  more  rapid  in 
contact  with  oxygen  or  air.  The  polymerization  of  isoprene  and  sim- 
ilar dienes  is  more  fully  discussed  in  a  separate  section  on  the  prop- 
erties of  unsaturated  hydrocarbons. 

As  regards  the  preparation  of  the  dienes,  it  is  possible  to  note 
processes  which  are  of  industrial  promise  and,  processes  which  are  not 
likely  to  become  commercial  on  account  of  the  cost  of  raw  materials  or 
operating  difficulties,  or  both. 

10  Harries,  Ber.  yt,  784    (1914). 

11  Cf.  J.  Russ.  Phys.-Chem.  Soc.  47.  1928  (1915). 
"Phil  Trans.  150,  254    (1860). 

aCompt.  rend.  89,  361,  1117   (1879). 
l*Chem.  News.  L6,  220    (1882). 
lsChem.  Neics,  65.  265   (1892). 
» Ann.  227,  295    (1885). 


216       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

The  earlier  workers  prepared  isoprene  by  the  destructive  distilla- 
tion of  rubber,  a  typical  distillation  yielding  the  following  products: 

Isoprene   6.2  per  cent 

Dipentene  46.0    "      " 

Higher  boiling  oils  43.8    ' 

Carbonized  residue   1.9    ' 

Loss  and  mineral  matter 1.9    ' 

The  formation  of  isoprene  by  pyrolysis  of  turpentine  was  first 
noted  by  Hlasiwetz  17  who  passed  turpentine  through  a  "red-hot"  iron 
tube  packed  with  broken  porcelain.  A  large  number  of  products  were 
obtained  and  isoprene  was  not  then  actually  identified  in  the  low  boil- 
ing fraction,  but  Tilden18  later  repeated  this  work  and  proved  the 
formation  of  isoprene  in  this  manner.  The  yields  of  isoprene  obtained 
by  the  pyrolysis  of  turpentine  and  dipentene  vary  greatly  and  are  gen- 
erally very  low.  Harries  19  obtained  10  per  cent  of  isoprene  by  decom- 
posing commercial  pinene  by  means  of  his  isoprene  lamp  (wires  heated 
electrically  to  low  red  heat) .  Herty  and  Graham  20  reported  yields  of 
5.5  to  8  per  cent  from  turpentine  fractions,  and  12  per  cent  from 
limonene  while  Harries  obtained  yields  of  30  to  50  per  cent  from  the 
latter  hydrocarbon.  By  decomposing  under  reduced  pressure,  4  mm., 
yields  as  high  as  60  per  cent  are  said  to  be  possible  from  limonene.21 
Schorger  and  Sayre  22  also  report  low  yields  from  turpentine,  the  two 
pinenes,  a  and  (3,  giving  substantially  the  same  yields.  Very  little 
attention  has  been  paid  to  the  temperature  required  for  optimum 
yields  of  isoprene  but,  in  contact  with  glass  or  porcelain,  this  tem- 
perature appears  to  be  550°  to  600°  ,23  According  to  Ipatiev,  the  con- 
densation of  isoprene  to  dipentene  is  fairly  rapid  at  300°. 

Small  yields  of  butadiene  and  isoprene  can  also  be  obtained  by  the 
pyrolysis  of  petroleum  oils  and  have  been  identified  in  the  low  boiling 
fractions  of  the  light  oils  obtained  by  compressing  oil  gas  or  Pintsch 
gas  to  150  to  200  pounds  pressure.  However,  the  fact  that  they  have 
been  detected  in  these  pyrolytic  products  is  a  tribute  to  the  analytical 
skill  of  the  chemists  who  investigated  these  hydrocarbon  mixtures.24 
Nevertheless,  the  preparation  of  isoprene  and  butadiene  by  the  pyroly- 

"  Ber.   9,  1991    (1876). 

18  J.  Chem.  Soc.  45,  410   (1884). 

18  Ann.  383,  228    (1911). 

20«7.  Ind.  &  Eng.  Chem.  6,  803  (1914). 

21  Staudinger  &  Klever,  Ber.  44,  2212    (1911). 

22  J.  Ind.  &  Eng.  Chem.  11,  924   (1915). 

2»Mahood,  J.  Ind.  <€  Eng.  Chem.  12,  1152  (1920);  Heinemann,  Brit.  Pat.  14,040; 
24,236  (1910);  1953  (1912);  Stephen,  U.  S.  Pat.  1,057,680;  Ostromuislenski,  French 
Pat.  442,980  (1912)  ;  Sobering,  German  Pat  260,934  (1913). 

34  Armstrong  &  Miller,  J.  Chem.  Soc.  49,  74   (1886). 


POLYMERIZATION  OF  HYDROCARBONS  217 

sis  of  petroleum  oils  at  about  700°,  particularly  in  vacua,25  has  re- 
cently been  patented.  This  method  presumably  would  give  better  re- 
sults with  light  petroleum  oils  containing  cyclohexane,  cyclopentane, 
and  their  simpler  homologues,  since  it  has  been  claimed  that  tetra- 
hydrobenzene  yields  a  certain  proportion  of  butadiene  on  decomposition 
under  these  conditions.26  However,  in  the  ten  years  which  have  elapsed 
since  this  work  was  done,  there  have  been  no  industrial  developments 
along  this  line  and  considering  the  small  yield  of  the  desired  dienes, 
the  value  of  petroleum  oils  for  other  uses,  and  the  difficulty  of  purify- 
ing the  desired  hydrocarbons,  it  is  very  doubtful  indeed  if  the  direct 
pyrolysis  of  hydrocarbons  will  ever  prove  to  be  an  economic  method 
of  producing  these  hydrocarbons.  In  this  connection,  it  should  be 
noted  that  Ostromuislenski 27  has  shown  that  on  polymerizing  iso- 
prene  containing  amylene  or  similar  defines,  the  resulting  "rubber"  is 
very  sticky  and  soft. 

Petroleum  pentane  is  mostly  normal  pentane  but  attempts  have 
been  made  to  utilize  this  hydrocarbon  as  a  raw  material  for  the  manu- 
facture of  isoprene.  It  may  be  said  of  all  the  chemical  methods  for 
the  preparation  of  these  unsaturated  hydrocarbons  that  no  really  new 
methods  or  reactions  have  been  developed;  all  of  the  known  methods 
of  producing  unsaturated  hydrocarbons  have  been  applied  to  the  prepa- 
ration of  these  dienes  but  the  great  majority  involve  the  elimination  of 
halogens,  usually  chlorine,  or  of  hydroxyl  groups  in  the  form  of  water. 
The  production  of  isoprene  from  normal  pentane  involves  the  change 
to  the  carbon  structure  of  isopentane.  This  is  accomplished  by  one 
patentee  28  by  taking  advantage  of  the  isomerization  of  defines  effected 
by  heat,  which  has  already  been  noted  in  the  case  of  the  butylenes. 
Thus  pentane  is  chlorinated  to  a  mixture  of  the  monochlorides  and 
these  are  converted  to  amylenes  by  pyrolysis  in  contact  with  barium 
chloride,  lime  or  other  methods,  and  the  mixture  of  amylenes  then 
passed  over  alumina  at  about  450°.  Partial  rearrangement  to  tri- 
methylethylene  occurs  and  on  treating  the  resulting  mixture  of  amyl- 
enes with  hydrogen  chloride  this  hydrocarbon  reacts  most  readily,  the 
chloride  thus  formed  being  separated  by  fractional  distillation.  The 
hydrocarbons  thus  separated  are  passed  again  over  alumina  at  450°, 
and  so  on.  The  purified  monochloroisopentane  is  converted  to  tri- 
methylethylene  by  the  usual  methods  and  this  treated  with  chlorine  to 

25Engler  and  Staudinger,  Ber.  46,  2468   (1913)  :  German  Pat.  265,172   (1912). 
28  Farbenfabr,  Elberfeld,  German  Pat.  241,895. 

27  J.  Russ.  Phys.-Chem.  Soc.  48,  1071   (1916)  ;  Chem.  Abs.  11,  1768   (1917). 
28Badische,  German  Pat.  280,596   (1919). 


+ HC1 


218      CHEMISTRY  Of  THE!  NON-BENZENOID  HYDROCARBONS 

form  the  dichloride  which  then  forms  isoprene  with  the  elimination  of 
two  molecules  of  hydrogen  chloride.  The  reactions  involved  are  as  fol- 
lows: 

CH3CH2CH2CH2CH3  -      >  monochlorides  -      > 

rCH3 

>C  =  CHCH, 
amylenes  -      >  4  CH 

4 
l_     and  isomers 

CH3 

>CC1.CH2CH3- >CH3 

CH.  >C  ==  CHCH3 

CH3 

(pure) 

CH. 

>  CC1 .  CHC1 .  CH3 >  CH2 

CH3  Y-CH  =  C 

CH3 

Petroleum  pentane  is  one  of  the  cheapest  raw  materials  which  have 
been  suggested  for  this  purpose  but  the  process  involves  a  large  num- 
ber of  operations,  distillations,  purification  of  intermediates  and  the 
losses  are  large,  for  example,  if  each  operation  indicated  above  gave  a 
yield  of  90  per  cent  the  final  net  yield  of  isoprene  would  be  about  ±7 
per  cent.  Pentane  can,  in  fact,  be  chlorinated  to  monochloropentanes 
with  a  yield  of  about  90  per  cent,  exclusive  of  vaporization  losses,  but 
the  losses  on  isomerizing  the  amylenes  are  large  and  it  is  impossible 
to  chlorinate  trimethylethylene  without  partially  chlorinating  further 
to  trichlorides  and  tetrachlorides. 

Several  patented  processes  employ  phenol  and  cresols  as  raw  ma- 
terials. Phenol  may  be  hydrogenated  to  cyclohexanol,  with  good 
yields,  and  this  alcohol  may  then  be  dehydrated  by  heating  in  contact 
with  alumina,  thoria  or  kaolin,  to  give  cyclohexene.  Cyclohexene  gives 
small  yields  of  butadiene  and  ethylene  by  direct  pyrolysis, 

CH2 

H2C  CH 

|       >  CH2  —  OH  —  CH  =  CH2  +  C2H4 

H2C  fcH 

CH, 


POLYMERIZATION  OF  HYDROCARBONS  $1$ 

Chlorination  of  cyclohexene  to  the  dichloride,  and  then  decomposing 
this,  yields  the  conjugated  diene,  cyclohexadiene,  but  this  hydrocarbon 
polymerizes  to  a  substance  more  nearly  resembling  resin  than  rubber. 
Benzene  itself  is  readily  hydrogenated  to  cyclohexane  and  this  may  be 
converted  to  cyclohexene  through  the  monochloro  derivative  by  the 
usual  methods  29  but  none  of  these  materials  yield  final  products  of 
good  quality. 

It  is  much  easier  to  prepare  isoprene  and  butadiene,  and  in  much 
purer  condition,  by  using  butyl  or  isoamyl  alcohol  as  the  raw  ma- 
terials. A  new  method  for  the  manufacture  of  n. butyl  alcohol  has 
been  developed  based  upon  the  fermentation  process  of  Fernbach,30 
the  two  principal  products  being  n. butyl  alcohol  and  acetone.  Al- 
though originally  developed  in  connection  with  the  synthetic  rubber 
problem  it  was  carried  out  on  a  large  scale  during  the  recent  war, 
essentially  as  a  process  for  the  manufacture  of  acetone.  At  com- 
paratively high  temperatures  butyl  alcohol  is  decomposed  partially  to 
butadiene 31  but,  as  in  many  pyrolytic  processes,  the  yields  are  small. 
The  alcohol  may  be  converted  to  the  corresponding  chloride  and  the 
resulting  butyl  chloride  then  chlorinated  to  the  dichlorides  which  may 
then  be  decomposed  by  methods  already  mentioned,  to  butadiene,32 

CH3CH2CH2OH >  CH3CH2CH2C1 »  dichloride >  butadiene 

By  similar  methods  isoamyl  alcohol,  the  chief  constituent  of  fusel  oil, 
may  be  converted  by  hydrogen  chloride  to  isoamyl  chloride,  which  on 
chlorination  yields  a  mixture  of  dichlorides, 

(CH3)2CH.CHC1.CH2C1  boiling-point     142°  C. 

(CH3)2CC1.CH2CH2C1  "  152°  C. 

CH2C1 

>CH.CH,.CH2C1  170°  C. 

CH3 

Of  these  dichlorides  the  second  is  the  principal  product,  but  the  crude 
mixture,  boiling-point  140°-180°,  is  used  for  the  production  of  isoprene, 
the  yield,  according  to  Perkin,33  being  40  per  cent  of  the  theory.  As 
pointed  out  by  Perkin  the  total  available  quantity  of  ordinary  fusel 
oil,  about  3500  tons,  is  wholly  inadequate  as  a  raw  material  for  rub- 

M  Schmidt,   Hochschwender  &   Eichler,   TL    S.   Pat.   1,221,382. 

w  Fernbach  &  Strange,  Brit.  Pat.  15,203;  15,209;  16,925  (1910).  The  butyl 
alcohol  contained  in  ordinary  fusel  oil  from  the  manufacture  of  alcohol  is  isobutyl 
alcohol  and  is  only  a  minor  constituent. 

31  Perkin  &  Mathews,  J.  Soc.  Chem.  Ind   82,  884  (1913). 

82  Cf.  Badische,  German  Pat.  255,519  (1913);  264,008  (1911);  Harries,  German 
Pat.  243,075;  243,076  (1910)  ;  Brit.  Pat.  18,653;  22,035  (1912). 

33  J.  Soc.  Chem.  Ind.  31,  616   (1912). 


220       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

ber  synthesis,  and  is  relatively  high  priced  on  account  of  its  many  in- 
dustrial applications.  The  per  cent  of  isoamyl  alcohol  in  commercial 
fusel  oil  varies  somewhat  according  to  the  distillation  range  over 
which  it  is  collected,  but  the  fraction  distilling  at  128°-131°  contains 
approximately  87  per  cent  isoamyl  and  13  per  cent  active  amyl  alcohol 
C2H5CH(CH3)  .CH2OH.  Two  typical  analyses  of  commercial  fusel 
oils  are  as  follows,34 

From  fermentation  Percent          From  fermentation  Percent 

of  potatoes  by  wt.  of  corn  by  wt. 

n.  Butyl  alcohol   .............      6.8  n-Propyl  alcohol  .............        3.7 

Isobutyl  alcohol  .............     24.3  Isobutyl  alcohol  .............     15.7 

Amyl  alcohols  ...............     67.8  Amyl  alcohols  ...............     75.8 

Fatty  acids  ..................         .04  Hexyl  alcohols  ..............      0.2(7) 

Fatty  acids  ...................  56 

It  is  probable,  in  view  of  the  researches  of  Ehrlich,35  that  such  varia- 
tions in  the  character  of  fusel  oils  are  due  to  differences  in.  the  yeasts 
employed  for  fermentation  or  proteins  otherwise  introduced  rather  than 
the  materials  fermented.  A  sample  of  fusel  oil  from  corn,  examined 
by  Pringsheim,36  contained  isopropyl  and  normal  butyl  alcohols  in  ad- 
dition to  the  normal  propyl  and  isobutyl  alcohols  which  are  normally 
present  in  fusel  oil  from  this  source. 

In  view  of  the  efforts  which  have  been  made  to  utilize  cheap  fer- 
mentable material  and  the  resulting  butyl  and  amyl  alcohols,  as  raw 
material  for  rubber  synthesis,  this  phase  of  the  work  is  reviewed  here. 
Ehrlich  claims  that  in  ordinary  yeast  fermentation  the  fusel  oil  alco- 
hols are  derived  from  the  decomposition  of  protein  material,  or  rather 
the  amino  acids  leucine,  isoleucine  and  the  like, 

NH2 

(CH3)2CH.CH2CH<  +  H20 

leucine  C0H 


2 


-  >  (CH3)2CH.CH2CH2OH  +  CO2  +  NH3 
isoamyl  alcohol. 

Ehrlich  established  the  following  relations, 

(1)  Pure  yeast  and  pure  sugar  yields  no  fusel  oil. 

(2)  "        "       "      "        "     +  leucine  yields  isoamyl  alcohol. 

(3)  "     +  isoleucine  yields  d.  amyl  alcohol. 

The  addition  of  ammonium  carbonate  or  asparagin  to  yeast  fermen- 
tations decreases  the  yield  of  fusel  oil  and  the  addition  of  leucine,  or 

«4  «The   Nitrocellulose   Industry",   Worden. 

86  Cf.  Brit.  Pat.  6,640  (1906)  ;  Ber.  40;  1027   (1907). 

"BiocJiem.  Z.  16,  243   (1909). 


POLYMERIZATION  OF  HYDROCARBONS  221 

protein  rich  in  this  complex,  increases  it.  Only  traces  of  fusel  oil  are 
formed  by  alcoholic  fermentation  by  means  of  Buchner's  cell-free 
pressed  yeast  juice.37  However,  normal  butyl  alcohol  at  least  can  be- 
come, under  certain  conditions,  one  of  the  principal  products  derived 
from  the  sugar  undergoing  fermentation.  Realizing  the  inadequacy  of 
the  supply  of  commercial  fusel  oil  for  possible  rubber  synthesis,  Per- 
kin  and  his  associates  undertook  to  develop  a  special  process  of  fermen- 
tation which  would  yield  larger  proportions  of  butyl  or  amyl  alcohols. 
Although  the  anaerobic  Bacillus  butylicus  was  discovered  by  Fitz  38  in 
1878  in  a  study  of  glycerine  fermentation,  and  Perdrix 39  had  described 
an  anaerobic  bacterial  fermentation  which  gave  very  high  yields  of 
fusel  oil,  it  does  not  seem  to  have  occurred  to  anyone  else  to  utilize  this 
possibility  until  it  had  been  developed  by  Fernbach  and  Strange.40  As 
has  been  previously  noted  both  the  major  products  of  this  fermenta- 
tion, acetone  and  n .  butyl  alcohol,  are  necessary  raw  materials  required 
by  several  different  processes  for  the  production  of  butadiene  and 
dimethyl  butadiene. 

All  of  the  known  methods  of  decomposing  alcohols  to  unsaturated 
hydrocarbons  have  been  applied  to  the  problem  of  producing  these  sim- 
ple conjugated  dienes.  Butyleneglycol  yields  butadiene  when  passed 
over  heated  kaolin,  alumina,  or  aluminum  phosphate.41  The  butylene- 
glycol,  required  by  this  process,  can  be  made  from  acetaldehyde,  the 
primary  raw  material  therefore  being  ethyl  alcohol  or  acetylene.  Acet- 
aldehyde may  be  condensed  by  well-known  methods  to  aldol,  which 
upon  reduction  yields  butylene  glycol, 

Alcohol,  or  acetylene  — >  acetaldehyde — >  CH3CH(OH)  .CH2CHO 
-+  CH3CH  (OH) .  CH2CH2OH  — *  CH2  =  CH .  CH  =  CH2 

Butyraldehyde  yields  a  certain  amount  of  butadiene*  when  passed  over 
kaolin  at  500°-600°  under  reduced  pressure 42  and  isovaleric  aldehyde 
yields  some  isoprene  under  the  same  conditions.43  Secondary  butyl 
alcohol  can  be  prepared  by  (1),  reduction  of  the  commercial  solvent 
methyl  ethyl  ketone,  derived  from  "acetone  oil,"  or  (2),  treating  oil 
gas  with  80  per  cent  sulfuric  acid  and  hydrolysing  the  butyl  hydrogen 

37Buchner  &  Meisenheimer,  Ber.  39,  3201  (1906). 
™Ber.  11,  481,  878  (1878). 
39  Z.  Spiritusind.  14,  177   (1891). 
*°  French  Pat.  488,364   (1913). 

"Mathews,  Strange  &  Bliss,  Brit.  Pat.  3,873  (1912);  Cf.  Bayer,  German  Pat. 
261,642  (1913). 

«2U.  S.  Pat.  1,033,327. 
«U.  S.  Pat.  1,033,180. 


222       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

sulfate  so  formed.  The  secondary  butyl  alcohol  may  then  be  decom- 
posed catalytically,  with  very  good  yields,  to  butylene,  which  on 
chlorination  or  bromination  and  subsequent  decomposition,  yields  bu- 
tadiene. As  has  already  been  noted,  it  is  very  difficult  completely  to 
remove  halogens  from  such  substances  on  account  of  the  stabilizing  in- 
fluence of  an  adjacent  double  bond,  the  second 

( 1 )  CH3CHBr .  CHBr .  CH3  -     -- >  CH3CHBrCH  =  CH2 

(2)  CH3CHBr .  CH  =  CH2  -     ~*  CH2  =  CH  —  CH  =  CH2 

reaction  taking  place  with  difficulty  (higher  temperatures)  and  when 
the  temperatures  are  sufficiently  high  for  the  complete  removal  of  halo- 
gen, loss  of  the  desired  diene  occurs  through  secondary  reactions. 

The  condensation  of  acetaldehyde  and  ethyl  alcohol  by  passing  over 
heated  copper,  followed  by  decomposition  of  the  condensation  product 
by  passing  over  heated  alumina,  has  been  noted  by  Ostromuislenski 44 
as  a  possible  method,  and  the  chemical  changes,  which  really  involve 
five  consecutive  reactions,  may  be  summarized  as  follows: 

2C2H5OH  ->  CH3CHO  +  C2H5OH  ->  CH2  =  CH.CH  =CH2  +  2H20 

The  yields  of  butadiene  are  poor  and  considering  the  number  of  other 
reactions  which  also  occur  in  this  process,  it  is  not  likely  to  become 
of  industrial  interest. 

That  tertiary  alcohols  are  much  more  easily  decomposed  to  un- 
saturated  hydrocarbons,  than  secondary  and  primary  alcohols,  is  well 
known,  and  advantage  is  taken  of  this  fact  in  the  employment  of 
pinacone  as  an  intermediate  product.  Thus  acetone  may  be  reduced 
and  condensed  to  pinacone  under  a  wide  range  of  conditions  and  the 
use  of  amalgams  for  this  purpose  is  particularly  promising.45  Pinacone 
is  smoothly  decomposed  by  passing  over  alumina  at  about  400°  giving 
good  yields  of  dimethylbutadiene.46 

acetylene 

acetate  of  lime  >      acetic  acid 


starches  and  sugars 
starches  and  sugars 

**J.  Ruas.  Phys.-Chem.  800.  W,  1472,  1494  (1915)  ;  ,7.  Chem.  Soc.  Abs.  1916,  I,  4. 
"Holleman,  Rec.  trav.  chim.  25,  206   (1906)  ;  Bull.  soc.  cMm.  1910,  454. 
«•  German  Pat.  250,086. 


POLYMERIZATION  OF  HYDROCARBONS  223 

CH3  CH3  CH2  CH2 

o-c        -,       \_c7/ 


dimethylbutadiene 

The  synthetic  rubber  manufactured  in  Germany  during  the  recent  war 
was  made  from  pinacone  and  dimethylbutadiene,  the  latter  material 
being  polymerized  in  sealed  iron  drums  during  a  period  of  several 
months. 

Pinacone  chlorohydrin  also  yields  dimethylbutadiene,  when  heated 
with  bases,  dimethylaniline  being  recommended  for  this  purpose,47  and 
Kondakow  48  claims  that  pinacone  dichloride  gives  better  yields  of  the 
diene  than  pinacone  itself.  Decomposition  of  the  alcohol  pentene-2, 
ol-4  by  passing  over  alumina  or  kaolin  at  400°  has  been  employed 
for  the  preparation  of  piperylene.  Under  certain  conditions  acetalde- 
hyde  condenses  to  crotonic  aldehyde  and  on  methylating  this  aldehyde 
pentene-2,  ol-4  is  formed. 

OH 
2CH3CHO  —  »  CH3CH  =  CH.CHO  —  *  CH3CH  =  CH.CH< 

CH3 

-*  CH3CH  =  CH.CH  =  CH2 

Many  methods  have  been  described  which  make  use  of  well-known 
syntheses,  but  which  are  interesting  from  a  theoretical  point  of  view. 
Kyriakides  49  has  described  an  interesting  synthesis  starting  with  chlo- 
roacetone,  which  is  ethylated,  and  the  resulting  chlorohydrine  is  then 
treated  with  caustic  alkali  to  obtain  the  oxide,  as  indicated  in  the  fol- 
lowing, 

CH3COCH2C1  -  >  CH3  CH3 

>C  —  CH2  -  >         >C  —  CH2 


Y 


"German  Pat.  319,505    (1916). 
48  J".  prakt.   Chem.  62,  169    (1900). 
WJ.  Am.  Chem.  Soc.  36,  663  (1914). 


CH3 

v 


224       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

The  oxide  is  decomposed  by  heating  in  the  presence  of  kaolin  at 
440°-460°. 

Dimethylallene  may  be  partially  converted  into  isoprene  by  re- 
arrangement 50  and  Ipatiev  51  has  prepared  isoprene  from  this  hydro- 
carbon by  adding  two  molecules  of  hydrogen  bromide,  followed  by  de- 
composing the  dibromide  by  well-known  methods, 

CH3  CH3 

>  C  =  C  =  CH2  +  2HBr »         >  CBr .  CH2CH2Br 

CH3  CH3 

CH2 
/-i OTT C*TT 

CH3 

Among  the  reactions  of  theoretical  interest  which  have  been  em- 
ployed in  research  in  this  field,  may  be  mentioned  Euler's 52  prepara- 
tion of  isoprene  by  the  exhaustive  methylation  of  methylpyrollidine,  as 
follows, 

CH3  — CH  —  CH2 

>NH  +  2CH3I  +  NaOH > 

H2  — CH2 

CH3  —  CH  —  CH2  CH3  —  C  ==  CH2 

|  >N(CH3)2I >  | 

CH2  —  CH2  CH2—  CH2— N  (CH8)  2 


•<TT  QTT 


+  KOH 

CH2  —  CH2  —  N(CH3)  8I >  CH3  —  C  ==  CH2 


nz: 

isoprene 

It  will  be  recalled  that  this  method  has  been  frequently  used  by  von 
Braun  and  others  in  the  investigation  of  alkaloids,  on  account  of  the 
ease  with  which  nitrogen  can  be  removed  from  organic  bases. 

Phenol  may  readily  be  hydrogenated  to  cyclohexanol,  which  on  oxi- 
dation by  nitric  acid 53  yields  adipic  acid.    Conversion  of  this  acid  to 

MWebel    (U.    S.    Pat.    1,083,164),    claims    that    as.    dimethylallene    rearranges    to 
isoprene  when  passed  over  alumina  at  300°,  and  preferably  under  diminished  pressure^ 
81 J.  prakt.  Chem.  55,  4  (1897). 
62  J.  prakt.  Chem.  57,  132   (1898). 
83  Bouveault  and  Locquin,  Bull.  Soc.  chim,  1908,  3t  437. 


POLYMERIZATION  OF  HYDROCARBONS  225 

the  amide,  followed  by  treatment  with  hypochlorite,  yields  tetramethyl- 
enediamine  and  the  method  of  exhaustive  methylation  applied  to  this 
diamine  yields  butadiene;  cresol,  treated  similarly,  yields  isoprene. 

Polymerization  of  Conjugated  Dienes  to  Rubber-like  Substances. 

As  pointed  out  elsewhere  in  these  pages  the  polymerization  of  iso- 
prene had  been  observed  by  Greville  Williams,  Bouchardat,  Tilden  and 
Wallach.  But  the  first  attempt  to  polymerize  isoprene  which  had  been 
prepared  from  sources  other  than  rubber  itself  was  Tilden's  investiga- 
tion of  isoprene  made  by  the  pyrolysis  of  turpentine,  published  in 
1888.54  Tilden  states  that,  "The  action  of  hydrochloric  acid  on  iso- 
prene converts  it  partially  into  caoutchouc ;  the  latter  seems  to  be  ob- 
tained more  easily  starting  with  the  oily  polymeride  resulting  from  the 
action  of  heat."  Some  28  years  later,  Ostromuislenski 55  showed  clearly 
that  the  character  of  synthetic  isoprene  rubber  was  markedly  affected 
by  the  method  of  polymerization;  that  on  heating  isoprene  to  80°-90° 
it  undergoes  spontaneous  polymerization  to  a  dimeride,  (3-myrcene,  and 
this  hydrocarbon  then  yields  "normal"  caoutchouc  when  polymerized 
by  sodium,  or  barium  peroxide.  However,  when  isoprene  itself  is 
treated  with  these  reagents  the  resulting  rubber  is  not  normal.56  Til- 
den seems  to  have  been  aware  all  along  that  rubber  might  be  formed 
by  the  polymerization  of  isoprene.  The  polymerization  of  the  isomeric 
hydrocarbon  piperylene,  CH3CH  =  CH  —  CH  =  CH2  had  been  ob- 
served by  Hofman 57  and  by  Schotten,58  but  their  publications  contain 
no  suggestion  that  their  product  resembled  rubber.  In  1892  Tilden,59 
in  a  communication  to  the  Philosophical  Society  of  Birmingham, 
stated,  "I  was  very  much  surprised  to  find  -that  the  contents  of  the 
flasks  containing  isoprene,  prepared  from  turpentine,  had  entirely  al- 
tered in  appearance.  Instead  of  a  colorless,  limpid  liquid,  there  was 
now  a  thick  syrup,  in  which  floated  several  pieces  of  a  yellow  solid 
material.  On  examining  it  more  closely  this  was  found  to  be  caout- 
chouc." *  *  *  "A  solution  of  synthetic  rubber  leaves,  on  evapora- 
tion, a  residue  which  completely  resembles  in  all  its  characteristics  a 
like  preparation  made  with  Para  rubber."  *  *  *  "Artificial  rub- 
ber combines  with  sulfur  in  the  same  way  as  natural  rubber,  giving 
an  elastic,  resistant  mass."  A  little  later  Tilden's  results  were  con- 

54  J.  Chem.  Soc.  45,  411  (1888). 

65  J.  Buss.  Phj/s.-Chem.  Soc.  48,  1071    (1916). 

"«7.  Ruse.  Phys.-Chem.  Soc.  47,  1928  (1915). 

"Ber.  Ik,  665   (1881). 

KBer.  15,  425   (1882). 

*»  Chem.  News.  65,  265  (1895). 


226       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

firmed  by  Weber60  who  prepared  about  200  grams  of  synthetic  iso- 
prene  rubber,  and  Pickles 61  also  confirmed  Tilden's  statement  that 
isoprene  polymerizes  on  standing  in  contact  with  air. 

The  marked  influence  of  oxygen  upon  the  formation  of  polymers  is 
well  shown  by  experiments  reported  by  Engler,62  in  which  duplicate 
samples  were  exposed  to  oxygen  and  carbon  dioxide,  at  80°  C.  The 
very  rapid  polymerization  of  styrene,  and  the  conjugated  dienes,  iso- 
prene and  myrcene,  are  particularly  noteworthy. 

PER  CENT  POLYMERS  FORMED  ON   STANDING. 

In  contact  with  COa  In  contact  with  0* 

Days  exposed  12841284 

Limonene    2%        4%        5%        8%       4%        6%        8%        9% 

Phellandrene    4  6  8  9  9         13         16         21 

Pinene   1  22  3  3  4  4  5 

Myrcene    8         13          18         22         20         30         40         50 

Camphene    3  4  5  6  5  7  8  9 

Isoprene 14  per  cent  in  10  hours;  35  per  cent,  10  hours 

Styrene 22  per  cent,  20  hours;      67  per  cent,  20  hours 

The  presence  of  moisture  apparently  has  no  effect  upon  the  rate  of 
polymerization  of  hydrocarbons,  although  the  smallest  trace  of  mois- 
ture acts  catalytically  upon  the  polymerization  of  the  aldehyde,  gly- 
oxal;63  monomolecular  succinic  dialdehyde  behaves  in  a  similar  man- 
ner. 

The  polymerization  of  dimethyl  butadiene,  dimethyl  2-3  buta- 
diene 1-3,  to  a  rubber-like  substance  was  first  effected  by  Kondakow,64 
who  noted  that  it  polymerized  spontaneously  and  more  rapidly  than  iso- 
prene or  butadiene.  His  publications  upon  the  polymerization  of  this 
dimethylbutadiene,  which  he  prepared  from  pinacone,  would  seem  to 
justify  Kondakow's  claims  of  priority,  so  far  as  the  dimethylbutadiene 
process,  later  patented  and  used  industrially  in  Germany,  is  concerned. 
It  was  noted  also,  and  confirmed  by  others,65  that  when  dimethyl 
butadiene  polymerizes,  either  spontaneously  or  in  the  presence  of  alco- 
holic caustic  potash,  a  dimeride  and  a  trimeride  are  produced,  in  addi- 
tion to  the  rubber-like  substance.  It  was  important  for  the  technicali- 
ties of  later  patent  controversies  that  Kondakow  had  described  his  di- 
methylbutadiene rubber  as  insoluble  in  most  organic  solvents,  although 
it  is  now  generally  recognized  that  this  property  varies  considerably 

"  J.  Boc.  Chem.  Ind.  13,  11   (1894). 

nJ.  Chem.  Soc.  97,  1085   (1910). 

93 8th  Int.  Congr.  Appl.  Chem.  25,  661   (1912). 

"Harries,  Ber.  40,  165   (1906)  ;  41,  255   (1908). 

64  J.  prakt.  Chem.  6//,  109  (1901). 

6BLebedew,   J.   Rues.   Phys.-Chem.   Soc.   $1,   1818    (1909);    Harries,   Ann.   S88,   210 


POLYMERIZATION  OF  HYDROCARBONS 


227 


with  all  rubbers,  depending  upon  the  degree  of  polymerization;  in  fact, 
vulcanization  is  essentially  a  process  of  effecting  higher  degrees  of 
polymerization.  It  is  well  known  also  that  dimethylbutadiene  poly- 
merizes more  rapidly  than  other  similar  hydrocarbons.  Perkin  states, 
"The  situation  in  1906  might  be  summed  up  in  this  way;  it  had  been 
recognized,  in  a  more  or  less  general  way,  that  most  compounds  con- 
taining a  system  of  conjugated  double  linkings,  show  a  tendency  to 
polymerize,  more  or  less  readily.  The  polymerides  are  either  viscous, 
ill  defined  substances,  or  well  characterized  caoutchoucs;  or,  again, 
hard  resinous  solids,  like  polystyrene.  Their  properties  vary  accord- 
ing to  their  method  of  preparation,  and  according  to  the  molecular 
weight  of  the  hydrocarbon  employed  as  a  raw  material." 

Like  natural  Para  rubber,  Kondakow's  rubber  can  be  depolymer- 
ized  by  heat,  although  more  readily  than  Para  rubber,  the  principal 
product  being  a  dimeric  dimethylbutadiene  resembling  dipentene  and 
which  Richard 66  and  Kondakpw  regard  as  having  the  structure, 

CH3 


or 


The  same  hydrocarbon  is  also  formed  by  careful  polymerization  of 
2.3-dimethylbutadiene-(1.3).  In  the  polymerization  of  isoprene  to 
synthetic  isoprene  rubber  a  dimeric  isoprene  is  formed,  in  addition  to 
the  dimeride,  dipentene.  This  second  hydrocarbon,  called  di-isoprene 
or  myrcene  by  earlier  writers,-  yields  a  liquid  tetrabromide,  in  con- 
trast to  the  crystalline  dipentene  tetrabromide.  According  to  Lebedew 

"Compt.  rend.  153,  116  (1911)  ;  According  to  Lebedew  and  Mereshkowski  (J.  Buss. 
Phys.-Chem.  Soc.  45,  1249  [1913])  this  dimeride  has  the  following  properties;  boiling- 
point  85°  at  13  mm.,  205°  at  750  mm.,  D|-O  0.8741  nD  1.48074 ;  dry  HC1  yields  a 

Me 

//C.Me.CHa  / 

monohydrochloride  MeC  >C.Me.CCl      ,  boiling  at  122°-124°  under  17  mm. ; 

T  \CH2CH2  \ 

Me 

oxidation  by  benzoyl  peroxide,  according  to  Prileschajev  (q.v.)  yields  a  dioxide  which 
is  hydrolyzed  by  aqueous  benzoic  acid  to  a  tetrahydric  alcohol* 


228      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

and  Mereshkowski 67  this  hydrocarbon  is  1 . 3-dimethyl-3-ethenyl-A6- 
cyclohexene.68  On  hydrogenating  in  the  presence  of  platinum  the  side 
chain  ethenyl  group  is  first  saturated,  following  the  general  behavior 
of  substances  containing  double  bonds  in  both  the  ring  and  side  chain. 


Piperylene  similarly  should  yield  two  dimerides.  Butadiene  yields  a 
dimeride,  C8H12,  boiling  at  36°  under  23  mm.,  129.5°-131°  under 
760  mm.  pressure.  Hydrogenation  by  PaaPs  method  yields  ethyl  cy- 
clohexane;  bromine  reacts  to  form  a  tejrabromide  melting  at  69.5°- 
70.5°  and  oxidation  yields  the  acid 


from  which  facts,  and  reasoning  by  analogy  from  the  relations  between 
isoprene  and  dipentene,  Lebedew 69  concludes  that  the  hydrocarbon  is 
1  -ethenyl-  A4-cy  clohexene, 


CH  —  CH, 


CH 


\ 


CH.CH^CH. 


CH2  — CH2 

These  details  are  of  first  importance  as  the  yield  of  synthetic  rubber, 
by  present  methods  of  polymerization,  is  seriously  diminished  by  the 
formation  of  these  oily  polymers. 

As  to  why  or  how  sodium  effects  the  polymerization  of  isoprene, 

mLoc.  cit. 

«Cf.  Harries,  Arm.  383,  157   (1911). 

69  J.  Ruas.  Phys.-CTiem.  8oc.  ±S,  1124   (1911). 


POLYMERIZATION  OF  HYDROCARBONS  229 

no  one  has  hazarded  a  theory.  Perkin70  relates  that  Weizmann  and 
Mathews  were  induced  to  try  the  effect  of  permitting  the  hydrocarbon 
to  stand  in  contact  with  the  metal,  by  their  having  noted  the  conversion 
of  dimethylallene  to  isopropylacetylene  by  metallic  sodium, 


(CH3)2C  =  C  =  CH2  (CH3)2CH  —  C^ 

a  reaction  which  had  been  recorded  by  Favorsky.71  This  discovery, 
the  polymerization  of  isoprene  by  sodium,  was,  according  to  Perkin, 
made  by  Weizmann  and  Mathews  in  July  and  August,  1910,  although 
it  was  first  publicly  described  in  the  following  year  by  Harries.72  The 
same  discovery  had  evidently  been  made  by  Harries  in  the  "em!  of 
(the  year)  1910." 

The  polymerization  of  hydrocarbons  may,  according  to  Lebedew 
and  Mereshkowski  73  be  grouped  in  several  well  defined  classes,  (1), 
the  styrene  type,  peculiar  to  ethylene  hydrocarbons  with  unsymmetri- 
cal  substitution  of  the  hydrogen  atoms  by  phenyl,  or  other  groups,  and 
yielding  amorphous  polymers  of  very  high  molecular  weight  and  whose 
structures  are  not  yet  known;  (2)  the  stilbene  type,  shown  by  sub- 
stances having  symmetrically  substituted  groups;  (3)  the  acetylene 
type,  whose  characteristic  is  the  formation  of  benzene  or  its  deriva- 
tives; (4)  the  allene  type,  yielding  cyclobutane  derivatives;  (5)  the 
1  .3-butadiene  or  isoprene  type,  which  forms  cyclohexane  derivatives 
and  also  polymers  of  high  molecular  weight,  usually  amorphous,  and 
including  rubber-like  substances.  The  structures  of  the  polymers  of 
the  styrene  and  stilbene  type,  when  ascertained,  may  show  that  these 
two  classes  are  really  of  the  same  type  of  polymerization. 

With  isoprene  and  2.3-dimethylbutadiene-(1.3)  it.  has  been  shown 
that  with  increasing  temperature  the  proportion  of  the  dimeride  in- 
creases and  that  of  the  rubber-like  polymer  decreases.  Since  the  re- 
action is  markedly  affected  by  catalysts,  it  follows  that,  for  maximum 
yields  of  "synthetic  rubber,"  a  catalyst  and  the  lowest  possible  temper- 
ature should  be  employed.  The  search  for  raw  materials  for  the  prepa- 
ration of  the  simpler  conjugated  dienes,  and  the  effort  to  discover  effi- 
cient methods  for  the  preparation  of  these  hydrocarbons  has  involved 
a  great  deal  of  research.  The  finishing  step  in  the  process,  polymeri- 
zation, is  still  without  a  theory  sufficiently  tangible  or  plausible  to  be 
of  use  as  a  guide  for  further  work.  There  has  been  a  very  noticeable 

70Loc.  cit. 

"  J.  Russ.  Phys.-Chem.  Soc.  19,  558  (1887). 

«  Ann.  S83,  157    (1911). 

"  J.  Russ.  Phys.-Chem.  Soc.  45,  1249   (1913)  ;  J.  Chem.  Soc.  Alts.  1913,  I,  1285. 


230      CHEMISTRY  OF  THE  NON-BENZEN01D  HYDROCARBONS 

abatement  of  research  on  rubber  synthesis  since  1912  (the  manufacture 
of  synthetic  rubber  may  have  been,  for  Germany,  a  war  preparedness 
measure) .  It  is  certain  that  all  methods  of  synthesis  previously  known 
have  been  applied  to  this  problem, — and  synthetic  rubber  has  not  yet 
made  a  place  for  itself.  New  methods  of  synthesis  or  polymerization, 
or  changed  economic  values  with  respect  to  raw  materials  for  synthe- 
sis, or  cost  of  plantation  rubber,  may  affect  the  situation  in  ways 
which  none  can  now  foresee. 


POLYMERIZATION  OF  HYDROCARBONS 


231 


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232      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


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Chapter  VII.     Cyclic  Non-benzenoid 
Hydrocarbons. 

General  Methods  of  Synthesis  of  Cyclic  Non- 
benzenoid    Hydrocarbons. 

Many  of  the  well-known  condensation  reactions  of  the  paraffine 
series  can  take  place  with  intramolecular  condensation  or  ring  forma- 
tion. Thus  the  type  condensation  of  acetic  ester  to  acetoacetic  ester 
can  take  place  with  the  diethyl  esters  of  adipic,  pimelic  and  suberic 
acids  to  form  5,  6  and  7  carbon  rings,  respectively,  for  example, 

CH2CH2 .  C02C2H5  CH2  —  CH., 

CH2<  CH2<  ">CO 

CH2CH2 .  C02C2H5  CH2  —  CH .  C02C2H5 

Glutaric  and  succinic  esters  do  not  condense  in  this  manner  to  give 
cyclobutane  and  cyclopropane  derivatives,  illustrating  the  relative  dif- 
ficulty with  which  ring  structures  of  3  or  4  carbon  atoms  are  formed. 
The  calcium  salts  of  adipic,  pimelic  and  suberic  acids  give,  on  heating, 
cyclopentanone,  cyclohexanone  and  cycloheptanone  respectively,  but 
calcium  succinate  gives  the  cyclic  diketone 

CH2  — CO  — CH2 

CH2  — CO  — CH2 

When  the  calcium  salt  of  cyclohexane  -1.3-dicarboxylic  acid  is  decom- 
posed by  heat  the  bicyclic  ketone  is  formed  which  Stark x  calls  "deme- 
thylated  pinone." 


melting*"'  /nt  170' 


157°'158°'  d»  °'9322  '  semicarbazone 


233 


234       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

Ring  closing  incidental  to  Grignard's  synthesis  of  carboxylic  acids  has 
been  observed,  as  in  the  case  of  1 . 5-dibromopentane,  which  with  mag- 
nesium forms  the  dimagnesium  compound,  and  then  on  treating  with 
carbon  dioxide  yields  cydohexanone  and  pimelic  acid.2 

Succinic  ester  and  sodium  condense  to  give  a  six  carbon  ring,  suc- 
cinosuccinic  ester.  On  hydrolyzing  and  heating  with  sulfuric  acid  the 
cyclic  diketone  is  obtained  which  may  be  reduced  to  cyclohexane  by 
converting  it  first  into  the  alcohol,  cyclohexanediol-1.4,  then  into  the 
corresponding  iodide  and  reducing  this  with  zinc  dust  and  acetic  acid, 
exactly  as  in  the  case  of  aliphatic  alcohols  and  iodides. 


Nc^     *.  ^ 

H^rY  Hi 


"^  Cyclohexane 


The  method  of  Wiirtz  and  Fittig,  of  treating  alkyl  halides  with  me- 
tallic sodium  effecting  condensation  with  formation  of  sodium  halide, 
has  been  employed  for  ring  formation.  Freund  made  cyclopropane  by 
treating  trimethylene  bromide  with  sodium.3 

CH2Br  CH2 

CH2<  +  Na2 >  CH2<  I       +  2NaBr. 

CH2Br  CH2 

Methyl  cyclobutane  was  prepared  by  Perkin,  Jr.,  in  a  similar  way 
from  1.4  dibromopentane.4 

CH2  -  CHBr .  CH3  CH2  —  CH  —  CH3 

|  +Na2— >  I  I 

CH2-CH2Br  CH2-CH2 

'Grignard  &  Vignon,  Compt.  rend.  1U    1358   (1907> 

KlvcoV^ow  /%n25    (1882K     The  origi°al  material  for  this  synthesis,   trimethylene 
Ilycerine  dis^illation.m°n  commercial  P'odnct,  being  isolated  from  the  forerunning  in 

*J.  Chem.  8oc.  5S,  201   (1888)  ;  65,  599   (1894). 


CYCLIC  NON-BENZENOID  HYDROCARBONS  235 

and  cyclohexane  has  been  made  from  1 . 6-dibromohexane  and  sodium. 
Condensations  to  carbocyclic  derivatives  have  also  been  made  as 
indicated  by  the  following  synthesis ;  the  disodium  compound  of  acetone 
dicarboxylic  ester  being  treated  with  iodine 5  gives, 

C02R  C02R  C02R  C02R 

CHNa  +  I2  +  NaHC  CH  —  CH 

C0<  >CO >CO<  >CO 

CHNa  +  I2  +  NaHC  CH  —  CH 

C02R  C02R  C02R  CO,R 

Instead  of  using  free  iodine  or  bromine,  alkyl  halides  may  react 
with  sodium  malonic  ester  or  similar  sodium  compounds,  as  in  the 
following  syntheses  carried  out  by  W.  H.  Perkin,  Jr.6 

CH2Br  C02R  CH2         CO2R 

+  CH2<  +  2CH3ONa »  I     >C< 

CH2Br  C02R  CH2         C02R 

from  which  cyclopropane  monocarboxylic  acid  is  readily  made  by  loss 
of  C02  from  the  dibasic  acid. 

In  the  same  way  trimethylene  bromide  (1)  and  pentamethylene 
bromide  (2)  yield 

CH2 

( 1 )  >  CH2  <        >  CH .  C02H  cyclobutanecarboxylic  acid 

CH2 

CH2  —  CH2 

(2)  >CH2<  >CH.C02H     cyclohexanecarboxylic  acid 

CH2  — CH2 

The  above  syntheses  are  capable  of  considerable  variation  and  exten- 
sion as  the  following  syntheses  indicate: 

(1)     CH2C1      CH2(C02R)2  CH2  — CH(C02R)2 

+  +2C2H5ONa^| 

CH2C1      CH2(C02R)2  CH2  — CH(C02R)2 

CH2  —  CNa  (CO,R)  2  CH2  —  CH  (C02R)  2 

I  +  Br2-*I  -> 

CH2  —  CNa  (C02R)  2  CH2  —  CH  (C02R)  2 

CH,  — CH.C02H 


CH9  — CH. 


C02H 


•v.  Pechmann,  Ber.  SO,  2569  (1897). 
•Ber.  35,  2091   (1902). 


236       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

(2)  CH2-C(C02R)2 

CH2  —  CNa(C02R)2  /  \ 

CH2<  +  CH2I2-*CH2  CH2 

CHa-  CNa(C02R)2  \  / 

CH2  — C(C02R)2 

CH2  — CH.C02H 
->CH2<  >CH2 

CH2  — CH.CO.H 

Acetoacetic  ester  and  ethylene  bromide  yield  cyclopropyl  methyl  ke- 
tone  in  the  following  manner: 

CH  CH3 


CH2Br          CO  CO 

II  CH2     |  CH2 

CH2Br  +  H2C       +  2C2H5ONa-»   I     >C  -*   [     >CH.CO.CH3 

|  CH2     |  CH2 

C02R  C02R 

Polymerization  of  unsaturated  substances  sometimes  results  in  ring 
formation,  as  in  the  condensation  of  isoprene  to  dipentene  and  isoprene- 
rubber. 


r          J"; 

I"    .  v 

> 

en 

CH    CHi                        ^N 

XH2 

L                     J 

:" 

*C*^ 

Vinylacrylic  acid  also  polymerizes  readily,  in  the  following  man- 
ner,7 when  heated  with  barium  hydroxide. 

CH2  =  CH .  CH  =  CH .  C02H .  CH2 .  CH  =CH .  CH2 

CH2  =  CH.CH  =  CH.C02H.          ^CH2.CH  =CH.CH2 

The  Grignard  reaction  has  also  been  employed  to  effect  ring  closing 
as  in  the  preparation  of  1-methyl-l-hydroxycyclopentane  by  Zelinsky 
and  Moser.8 

TD8bner,  Ber.  S5,  2129  (1902). 
•Ber.  S5t  2684   (1902). 


CYCLIC  NON-BENZENOID  HYDROCARBONS 


237 


CH 


C  =  0  I                    C  =  0  Mgl 
CH2                CH2     CH2                CH2 
^CH       CH                   OTI 

CH 
>CH 

Aw 

OH" 
c 

/XCH 
2            ^H2 

L 

CH3  OMgl 

\  / 

C 

CH 


CH 


CH 


In  the  same  manner  that  acetone  condenses  to  give  mesityl  oxide, 
diacetylbutane  treated  with  sulfuric  acid  yields  methylcyclopentene- 
methyl  ketone.9 

CH2  — CH2  — CO  —  CH3  CH2  — C  — COCH3 

CH2<  >CH2<  || 


CH9  — CO  —  CH, 


CH, 


CH3 


Diacetylpentane  when  similarly  treated  yields  a  methylcyclohex- 
enemethyl  ketone. 


CH2 

CH 


\ 


C  —  COCH3 
C  — 


CH 


CH 


Condensation  of  alkyl  halides  with  benzenoid  hydrocarbons,  with 
elimination  of  halogen  acid,  takes  place  very  rapidly  in  the  presence 
of  anhydrous  aluminum  chloride  (the  Friedel-Crafts  synthesis).  This 
reaction  has  been  employed  for  ring  closing,  as,  for  example,  phenyl- 
valeryl  chloride  being  converted  into 


\i~c^ 


benzo- cycle  heptan  one 


•Kippin*  &  Perkin,  J.  CTiem.  Soc.  57,  14,  24  (1890). 


238      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

Halogen  acids  are  very  readily  eliminated  from  alkyl  chlorides 
alone,  when  treated  with  aluminum  chloride,  as  for  example,  chloro- 
pentanes  and  chlorohexanes,  but  the  nature  of  the  resulting  products 
has  apparently  never  been  investigated. 

Condensation  of  the  aldehyde  citronellal  to  isopulegol,  through  the 
action  of  acetic  anhydride,  is  not  typical  but  illustrates  the  tendency, 
so  frequently  observed,  to  form  rings  of  six  carbon  atoms. 
CH3  CH3 

CH  CH 

H2C  CH2  •H2C>'  CH2 

H2C          CHO  H2C          C< 

\  \   /      OH 

CH  C 

' 


.  . 

CH3          CH3  CH3          CH3 

citronellal  isopulegol 

Methylheptenone  is  condensed  by  dehydrating  agents  to  a  mixture 
of  m-xylene  and  1  .  3-dimethyl-A3-cyclohexene.  The  initial  reaction 
product  apparently  is  1.3-dimethyl-A1-3-cyclohexadiene,  which  it  will 
be  noted  has  the  same  arrangement  of  the  double  bonds  as  in  a-ter- 
pinene  and  the  ease  with  which  terpinene  is  converted  to  cymene  is 
well  known.  Apparently  this  cyclohexadiene  derivative  undergoes 
auto-reduction  to  give  about  equal  parts  of  m-xylene  and  1.3-di- 
methyl-A8-cyclohexene.10 

CH3  CH3 


/BE.  /  \ 

H2C  CH  H2C  CH 

H2C          C  —  CH3  H2C          C  —  CH3 

\  /  '   \  / 

C  C 

H  H 

The  condensation  of  pseudo-ionone  to  a  and  |3-ionone  by  means  of 
sulfuric  acid  is  supposed  to  take  place  through  the  addition  and  subse- 

10Wallach,  Ann.  395.  74   (1913). 


CYCLIC  NON-BENZENOID  HYDROCARBONS  239 

quent  loss  of  water.  The  discovery  of  this  reaction  (and  the  formation 
of  pseudo-ionone  from  citral  and  acetone  by  the  action  of  barium  hy- 
drate or  other  alkalies)  by  Tiemann  and  Kruger,11  in  1882  marked  the 
beginning  of  the  industrial  manufacture  of  this  now  well-known  "syn- 
thetic violet"  perfume.  The  two  ionones  are  cyclohexane  derivatives 
(see  p.  201). 

Pinacone  condensation  may  take  place  intramolecularly  to  form 
carbocyclic  structures,  as  for  example,  the  formation  of  1  .  2-dimethyl- 
1  .  2-dihydroxycycloheptane  from  diacetylpentane.12 

CH2  —  CH2  —  COCH3  CH2  —  CH2  —  COH  .  CH3 

CH2<  -  >CH,< 

CH2  —  CH2  —  COCH3  CH2  —  CH2  —  COH  .  CH3 


A  special  synthesis,  that  of  cyclopropane  derivatives,  has  been  ef- 
fected by  means  of  diazomethane  or  diazoacetic  ester  by  Buchner  and 
Curtius.13  Thus  fumaric  ester  and  diazomethane  yield  cyclopropane- 
dicarboxylic  ester. 


CH2      CH.C02R          CH2 CH.C02R  CH.C02R 

\   +11  ->  I  -^CH2<| 

=  N      CH.CO2R         N  CH.OXR  CH.C02R 


v 


Cyclopentanone  has  been  made  by  applying  the  method  of  con- 
densing nitriles  in  the  presence  of  sodium  ethylate,  a  reaction  discov- 
ered by  Thorpe.14  Thus  1 . 4-dicyano- valeric  ester  condenses  to  the 
imino  compound. 


CH2  —  CH2CN  CH2  —  CH2 .  CN 

2_CH-CN »  ( 

02R  CH2  — CH 


=  NH 


On  hydrolyzing  by  means  of  sulfuric  acid  and  heating  the  resulting 
acids  the  imino  group  is  replaced  by  oxygen  and  two  molecules  of  C02 
are  removed,  resulting  in  cyclopentanone. 


"Ber.  SI,  808  (1898). 

"Kipping  &  Perkin,  J.  Chem.  Soc.  59,  214  '1891). 

"Ber.  18,  237    (1885). 

"J.  Chem.  Soc.  85,  1726   (1904)  ;  91,  578,  1004   (1907). 


240      CHEMISTRY  OF 


CH2  — CH  — C02H 
C  =  NH 
)H2  —  CH 


NON-BENZENOID  HYDROCARBONS 

CH2  — CH, 


\ 


CO. 


CH2  — CH2 


CO  +  2  C02 


H 


It  has  been  shown  by  Thorpe 15  that  ring  closing  to  form  rings  of 
five  carbon  atoms  takes  place  very  rapidly  and  with  approximately 
equal  ease  in  both  the  following  cases, 


CH2CN 


C=NH 


.CH2CN  XH-CN 

CH2  — CH2CN  CH2  — CH2 

CH2  —  CH2CN  /  C  =  NH 

CH2  — CH  — CN 

Kon  and  Stevenson  also  find 16  that  ring  closing  by  elimination  of  wa- 
ter from  the  COOH  group  takes  place  readily  forming  products  of  the 
following  type. 

u 

R 


There  is  no  indication  of  the  valency  direction  being  different  in 
any  of  these  examples  of  ring  closing. 

An  instance  of  the  ease  with  which  substances  containing  a  five- 
carbon  ring  are  formed  is  the  condensation  of  si/m.-dipropionylethane 
to  l-methyl-5-ethyl-A5-cyclopentene-2-one  by  the  action  of  10  per  cent 
aqueous  caustic  potash.17 

"  J.  Chem.  Soc.  93,  165  (1908)  ;  95,  1901  (1909). 
"J.  Chem.  Soc.  119,  87   (1921). 
"Blaise,  Oompt.  rend.  158,  708   (1914). 


CYCLIC  NON-BENZENOID  HYDROCARBONS  241 

CH3CH2CO       H2C  —  CH3  CH3CH2C  =  =  C  —  CH3 


\ 

( 
—  CH2 


CO 


\ 
— CH 


CO 


Acetonylacetone  and  acetonylacetophenone  are  unchanged  under  these 
conditions. 

Kishner18  has  discovered  that  when  hydrazine  reacts  upon  un- 
saturated  ketones  containing  the  group  — CH  =  CH .  CO-pyrazoline 
bases  are  formed  in  many  instances,  which  are  readily  decomposed  to 
give  cyclopropane  derivatives.  Thus  pulegone  yields  carane: 


In  a  similar  manner,  isobutylidene  acetone  yields  l-methyl-2-iso- 
propyl-cyclopropane, 

Pr  Pr 

.  CH  —  CH,       HC- 


CH3 
CH, 


CH, 


>CH.CH  =  CH.COCH3  -»  HN< . 


N=C- 


CH 


\ 


+N2 
CH.CH3 


Cinnamic  aldehyde  yields  phenylcyclopropane  and  phorone  yields 
a  dimethylisobutenylcyclopropane.  This  synthesis,  discovered  by  Kish- 
ner, is  another  example,  illustrating  the  remarkable  reactivity  of  the 
group  _  CH  =  CH  —  CO  — . 

As  noted  above  cyclopropane  derivatives  are  formed  by  the  reac- 
tion of  diazoacetic  ester  and  olefine  bonds,  a  reaction  employed  by 
Buchner  to  throw  light  on  the  constitution  of  camphene.19 

»  J.  Ruse.  Phys.-Chem.  Soc.  40,  987  (1913)  ;  J.  Chem.  Soc.  Aba.  1913,  I,  1163,  1165. 
»Ber.  46,  759  (1913). 


242       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


(CHa), 


H-C02K 


The  formation  of  a  seven  carbon  ring  from  a  cyclohexane  derivative 
has  been  noted  in  the  reaction  of  mesitylene  and  diazoacetic  ester,  the 
intermediate  product  being  smoothly  decomposed  in  the  presence  of 
copper  powder  at  105°.  This  is  another  illustration  of  rearrangement 
which  undoubtedly  takes  place  through  the  intermediate  formation  of 
a  cyclopropane  derivative.20 


CH3  —  C=:=CH  —  C  —  CH3 

CH.C02C2H 
mesitylene  / 

+  CH  =  C  -  CH 

diazoacetic  ester  -» 


CH3 


CH3  —  C==CH  —  CH  —  CH3 

C.C02C2H5 
C Clt 


CH3 


The  formation  of  cyclic  non-benzenoid  hydrocarbons  by  hydrogena- 
tion  of  aromatic  hydrocarbons  is  a  useful  method  for  the  preparation 
of  a  limited  number  of  substances  and  these  could  very  properly  be 
given  the  appellation  hydroaromatic  compounds.  The  hydrogenation 
of  benzene  at  180°-200°  over  finely  divided  nickel  was  first  carried  out 
in  1901  by  Sabatier  and  Senderens,21  and  cyclohexane  made  in  this  way 
has  been  employed  to  some  extent  as  a  motor  fuel  for  aeroplanes.22  On 
hydrogenating  naphthalene,  tetrahydronaphthalene  is  the  principal 
product  at  180°-200°,  but  at  250°  and  120°  atmospheres  pressure  deca- 
hydronaphthalene  is  formed.  Tetrahydronaphthalene  has  recently 
become  an  industrial  product,  being  recommended  as  a  solvent  or  tur- 

20Buchner,  Ber.  53,  865  (1920). 
"Compt.  rend.  132,  210  (1901). 
22  CJ.  Brit.  Pat.  133,288;  133,667  (1919). 


CYCLIC  NON-BENZENOID  HYDROCARBONS  243 

pentine  substitute.23  The  xylenes  readily  yield  the  corresponding  di- 
methylcyclohexane,  p-cymene  is  converted  into  para-menthane,  and 
meta-menthane  is  easily  obtained  by  the  catalytic  hydrogenation  of 
sylvestrene.2*  Indene  at  250°  and  under  pressure  may  be  hydrogenated 
to  octahydrindene  or  bicyclononane.25 

CH2  —  CH2  —  CH  —  CH2 


[2_CH2  — CH  — CH2 

Dibenzyl  ketone,  made  from  phenylacetic  acid,  yields  dicyclohexyl- 
propane  on  hydrogenation  by  catalytic  nickel  and  hydrogen. 

Cyclic  Non-benzenoid  Hydrocarbons. 

As  pointed  out  in  the  preface,  it  is  difficult  to  classify  the  non- 
benzenoid  hydrocarbons  in  a  way  which  will  not  unduly  emphasize 
slight  differences  in  chemical  behavior  or  structure.  As  regards  chemi- 
cal behavior  we  should  certainly  consider  cyclopentane  with  normal 
pentane  and  cyclohexane  with  normal  hexane.  Also,  the  amount  of 
information  dealing  with  the  derivatives  of  cyclohexane  exceeds  the 
sum  total  of  that  dealing  with  all  the  other  cyclic  non-benzenoid  hydro- 
carbons. The  reasons  for  this  are  the  long  standing  interest  in  the 
chemistry  of  benzene,  the  conversion  of  benzene  and  a  few  of  its  de- 
rivatives to  cyclohexane  derivatives  by  hydrogenation,  and  the  avail- 
ability of  material  for  investigation,  as  in  the  case  of  the  terpenes. 
Practically  all  of  the  other  cyclic  non-benzenoid  hydrocarbons  have 
been  obtained  only  by  synthesis,  only  a  very  few  of  the  simplest  of 
such  hydrocarbons  having  been  isolated  from  petroleum.  Although  the 
quantity  of  information  regarding  cyclohexane  is  so  relatively  large, 
the  use  of  the  term  "hydroaromatic"  for  the  cyclohexane  series  is  very 
unfortunate  and  will  be  avoided  in  the  following  pages  as  much  as 
possible. 

Some  writers  may  consider  that  cyclopropane  may  properly  be  con- 
sidered together  with  ethylene  and  its  derivatives  but  the  so-called  un- 

M  Cf.  Tetralin  and  Similar  Hydrogenated  Products, — Frydlender,  Rev.  prod.  chim. 
23,  719  (1920). 

2«Sabatier  &  Marat,  Compt.  rend.  156,  184    (1913). 

"Ipatiev,  J.  Chem.  Soc.  Abs.  1913,  I,  1165;  Osterberg  &  Kendall,  J.  Am.  Chem.  Soc. 
ifi,  2616  (1920),  recommend  Ipatiev's  method  for  the  preparation  of  cyclohexane  from 
benzene.  The  method  consists  simply  in  placing  the  benzene  and  catalyst  in  a  tight 
bomb,  heating  to  250°  and  passing  in  hydrogen  at  1800  Ibs.  pressure  from  a  pressure 
cylinder. 


244       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

saturation  of  cyclobutane  places  it  close  to  cyclopropane  and  in  a  po- 
sition intermediate  between  cyclopentane  and  cyclopropane.  How- 
ever, some  concession  must  be  made  to  the  necessity  of  some  sort  of 
orderly  arrangement  of  subject  matter  and  the  writer  has  elected  to 
discuss  the  cyclic  non-benzoid  hydrocarbons  in  a  series  beginning  with 
cyclopropane. 

There  are  two  general  classes  of  information  regarding  the  cyclo- 
paramnes  and  particularly  the  cyclohexane  series.  On  the  one  hand 
there  is  a  relatively  large  amount  of  information  obtained  by  the  in- 
vestigation of  pure  substances,  either  synthesized  or  isolated  from  a 
natural  product  as  is  usually  the  case  in  the  study  of  the  terpenes ;  this 
information  is  usually  accurate  and  satisfactory,  from  a  scientific 
point  of  view.  The  second  type  of  information  is  much  less  definite 
and  less  reliable  and  has  to  do  with  very  imperfectly  known  mixtures 
such  as  petroleum  distillates,  shale  oils,  rosin  oils,  and  similar  products 
whose  literature  is  nevertheless  considerable  by  reason  of  their  com- 
mercial importance.  In  dealing  with  the  chemistry  of  these  substances 
the  scientific  and  industrial  works  have  usually  been  rigidly  exclusive, 
each  of  the  other  class  of  information.  However,  the  proportion  of 
information  of  permanent  scientific  value  contributed  by  the  indus- 
tries is  becoming  greater  than  ever  before  and  cannot  be  passed  by, 
and  in  the  following  pages  information  from  industrial  sources  will  be 
included  whenever  it  is  of  interest  and  appears  to  be  of  permanent 
scientific  value. 

Cyclopropanes:  Simple  cyclopropane  hydrocarbons  have  not  been 
found  in  nature  but  the  bicyclic  terpenes  sabinene  and  carene  possess 
three  carbon  rings,  as  does  also  the  ketone  thujone.  The  similarity 
of  the  cyclopropane  ring  to  the  ethylene  bond  has  repeatedly  been 
pointed  out.  Its  influence  upon  physical  properties  is  less  marked 
than  in  the  case  of  the  double  bond,  as  has  been  reviewed  in  the  sec- 
tion on  physical  properties.  Carr  and  Burt 26  conclude,  from  a  study 
of  absorption  spectra,  that  the  cyclopropane  ring  is  a  "center  of  resid- 
ual affinity"  similar  in  character  but  intermediate  in  quantity  to  that 
of  the  double  bond,  and  as  such  can  form  a  conjugated  system  with 
the  carbonyl  group.  The  relative  stability  of  the  derivatives  of  cyclo- 
propane varies  within  wide  limits,  with  different  substituent  groups, 
as  will  be  brought  out  in  the  following  pages. 

Kohler  and  his  students  have  shown,  in  a  series  of  papers,  that  sub- 
stituents  have  exactly  the  same  effect  upon  the  mode  of  addition  to  a 

*  J.  Am.  Ghem.  Soc.  40t  1590  (1918). 


CYCLIC  NON-BENZENOID  HYDROCARBONS  245 

cyclopropane  ring  as  to  an  ethylene  linkage,  even  though  the  saturated 
open-chained  compounds  formed  in  the  two  cases  are  quite  different  in 
structure.27  Thus,  as  pointed  out  by  Kohler  and  Conant,  the  mode  of 
addition  of  hydrobromic  acid  to  cyclopropane  hydrocarbons  is  deter- 
mined by  the  number  and  arrangement  of  the  alkyl  groups.  The  ring 
invariably  opens  between  the  carbon  atoms  that  hold  the  largest  and 
the  smallest  number  of  alkyJ  groups  and  the  principal  product  is  al- 
ways one  in  which  the  halogen  is  combined  with  the  carbon  atom  that 
holds  the  largest  number  of  alkyl  groups.  In  the  case  of  cyclopropane 
carboxylic  acids  the  C02H  groups  may  affect  the  ease  with  which  addi- 
tion takes  place,  but  the  product  is  always  either  a  y-bromo  acid  or 
the  corresponding  lactone.  The  few  ketones  that  have  been  studied 
behave  like  the  acids.  In  cases  where  a  carbonyl  group  is  next  to  the 
ring  the  halogen  atom  accordingly  always  goes  to  the  ^-position  in  the 
ring,  for  example, 

CH2 

|       >  CH .  C02H  +  HBr >  CH2Br .  CH2CH2 .  C02H 

CH2 

CH2 

>  CH .  CO .  C6H5  +  HBr »  CH2Br . 


Kohler  and  his  assistants  find  that  derivatives  of  the  type 
C6H5CH  —  CH.COC6H5 

C(C02R)2 

are  quite  stable  to  cold  permanganate  solution  and  to  ozone  but  are 
hydrolyzed  by  water  with  "unusual  rapidity,"  and,  in  the  absence  of 
water,  alcoholates,  ammonia  and  amines  rapidly  convert  them  into 
isomerJc  unsaturated  compounds. 

The  cyclopropane  ring  may  be  broken  in  different  ways  depending 
upon  the  conditions  and  the  reaction  employed.  The  phenylanisoyl 
derivative  studied  by  Miss  Hahn 28  breaks  down  in  the  three  ways 
indicated  below, 

(1)     With  alkali  alcoholates 

C6H5CH  —  CH .  COC6H4OCH3 

\ .  /  >  C6H5CH  =  C  —  COC0H,OCH8 


C(C02CH3)2  | 

"Cf.  Kohler  &  Conant,  J.  Am.  Chem.  8oc.  39,  1404   (1917), 
*»«/.  Am.  Chem.  8oc.  88,  1-320   (lOlrfi. 


H(C02CH3) 


246       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

(2)  When  the  dibasic  acid  is  heated  C02  is  evolved  accompanied  by 
rupture  of  the  ring, 

RCH  —  CH .  COC6H4OCH3 

\  :  /  >  RCH  =  C .  CH2COC6H4OCH3 

C(C02H)2  | 

C02H 

(3)  When  the  ester  in  solution  in  acetic  acid  is  reduced  with  zinc  dust 
the  reduced  derivate  is  obtained 

RCH  —  CH .  COC6H4COCH3 

\   /  »RCH.CH2COC6H4OCH2 

C(C02CH3)2  | 

CH(C02CH3)2 

A  series  of  cyclopropane  derivatives  has  been  made  by  Bruylants 29 
starting  with  the  novel  reaction, 

CH2Br  CH2Br 

CH2<  +  2C2H5MgBr >  CH2<  » 

CH2CN  CH2C  —  C2H5 

N.MgBr 
CH2 


CH 


CH2 


CH2<| 


CH  —  C  —  C2H5  CH  —  C  —  C2H5 

II  II 

NMgBr  O 

Halogen  derivatives  of  the  type    CH2  .      CH3 

|       >CHC< 
CH2  |     CH3 

are  quite  stable  to  boiling  aqueous  caustic  alkali  but  boiling  with  alco- 
holic alkali  gives  a  mixture  of  the  ether  and  the  unsaturated*  hydro- 
carbon. When  the  unsaturated  hydrocarbon  is  treated  with  bromine  a 
tribromide  is  formed,  the  double  bond  taking  up  Br2  and  the  tertiary 
hydrogen  atom  being  replaced  without  rupture  of  the  cyclopropane 
ring, 

CH2  CH2  CH2  CH2Br 

\               //  \  / 

CH  — C  +2Br0 »  C  — C.Br 


/I  \ 


CH2  CH3  CH2      f  CH3 

**Rec.  trav.  chim.  28,  180   (1909). 


CYCLIC  NON-BENZENOID  HYDROCARBONS  247 

Kohler  has  made  a  number  of  nitro  derivatives  of  cyclopropane  by  re- 
acting upon  unsaturated  substances  with  nitromethane,  brominating 
and  removing  HBr,  for  example,30 

C6H5CH  =  CH .  COC  (CHS)  ,'+  CH3N02^C6H5CH— CH2COC  (CH3) . 

CH2N02 

+  Br2 
>  C6H5CH  —  CHBr .  COC  (CH,) ,          +  CH3C02K. 

;H2N02 

C6H5CH  —  CH .  COC  (CH3) , 

CH.N02 

Cyclopropane  is  reduced  to  propane  by  hydrogen  and  catalytic 
nickel  slowly  at  80°  and  rapidly  at  120°,  but  cyclobutane  requires  a 
temperature  of  approximately  180°  for  hydrogenation  to  butane.81 
Cyclopropane  thus  occupies  a  position  intermediate  in  stability,  to 
hydrogen  and  nickel,  between  cyclobutane  and  ethylene,  the  latter 
being  reduced  to  ethane  at  temperatures  as  low- as  — 15°.  Cyclo- 
propane is  readily  reduced  to  propane  by  colloidal  platinum  in  acetic 
acid  but  cyclopropane- 1 . 1-dicarboxylic  acid  is  not  reduced  under  these 
conditions.32  Ethylene  is  reduced  a  little  more  rapidly  than  cyclopro- 
pane by  this  method  (Fokin-Willstatter  method) . 

In  contact  with  iron  conversion  of  cyclopropane  to  propylene 33  can 
be  observed  at  100°,  but  in  the  presence  of  platinum  black  the  reaction 
is  slow  at  200°,  although  rapid  at  315°. 

Cyclopropane  can  be  prepared34  by  the  reduction  of  1.3-dibromo- 
propane  by  zinc  in  alcohol  (75  per  cent)  at  temperatures  not  exceeding 
60°.  It  was  first  made  by  the  action  of  sodium  on  this  dibromide.  It 
is  thus  evolved  as  a  gas,  easily  condensed  to  a  liquid  boiling  at  —  35° 
(749  mm.). 

Methyl  Cyclopropane,35  boiling-point  4°  to  5°,  is  formed  when  1.3- 
dibromobutane  is  treated  with  zinc  dust  in  alcohol,  in  the  same  manner 
in  which  Gustavson  prepared  cyclopropane  from  1 . 3-dibromopropane. 

1 .1-Dimethylcyclopropane,56  boiling-point  21°,  like  other  deriva- 

10  Kohler  &  Rao,  J.  Am.  Chem.  Soc.  41,  1697   (1919). 

11  Willstatter  &  Bruce,  Ber.  W,  4459   (1907). 

12  Boeseken  and  others,  Rec.  trav.  chim.  35,  260  (1916). 
"Ipatiev,  Ber.  35,  1057   (1902)  ;  86,  2014   (1903). 
"Gustavson,  J.  prakt.  Chem.   (2)   76,  512   (1907). 
"Demjanoff,  Ber.  28,  22  (1895). 

"Ipatiev  &  Huhn,  Ber.  86,  2014  (1903). 


248       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

tives  of  cyclopropane,  reacts  only  very  slowly  with  permanganate,  and 
may  thus  be  distinguished  from  the  isomer  trimethylethylene,  the  lat- 
ter hydrocarbon  being  formed  when  1 . 1-dimethylcyclopropane  is 
passed  over  alumina  at  340°-345°. 

The  2.3-dicarboxylic  acid  derivative  of  1 . 1-dimethylcyclopropane 
is  of  interest  as  having  been  produced  by  Baeyer  and  Ipatiev 37  by  the 
oxidation  of  carone  and  later  synthesized  by  W.  H.  Perkin,  Jr.,  and 
Thorpe.38  It  exists  in  two  physically  isomeric  forms  known  as  cis  and 
frans-caronic  acids.  It  was  synthesized  by  treating  the  ester  of  mono- 
bromo-|3(3-dimethylglutaric  acid  with  alcoholic  caustic  potash. 

C(CH3)2 

/  \  C(CH3)2 

/         \  KOH  /  \ 

C2H502C.CHBr    CH2.C02C2H5  -       — >  KO2C . CH  —  CH . CO2K 

Hydrobromic  acid  at  100°  breaks  the  ring  in  the  following  manner: 

C(CH3)2 

\/  \  Br.C(CH3)2 

/\      \  +HBr  | 

H02C .  CH  —  CH .  C02H  -        --»  H02C .  CH2  —  CH  —  C02H 

The  alkali  salts  of  cis  and  trans-caronic  acids  are  quite  stable  to  aque- 
ous permanganate. 

1  .@.-Dimethylcyclopropane  has  been  made  from  2 . 4-dibromopen- 

0°  20° 

tane  by  Gustavson's  method.    It  boils  at  32°-33°,  d  -^  0.7025,  d  — 

10° 
0.6806,  n^-  1.3823. 

1 .2.3.-Trimethylcyclopropane  was  made  by  first  synthesizing  3- 
methylpentanediol-(2.4).  This  was  converted  to  the  corresponding 
dibromide  by  heating  with  hydrobromic  acid  and  the  dibromide  treated 
with  zinc  dust  in  80  per  cent  alcohol,  yielding  the  hydrocarbon,  boiling- 

22°  22° 

point  65°-66°,d—    ,  0.6921,  n^jyl. 3942.    It  is  quite  stable  to  aqueous 

permanganate. 

1 .1 .2.-Trimethylcyclopropane  was  made  by  Kishner39  from  mes- 
ityl  oxide  by  his  hydrazine  method.  The  hydrocarbon  boils  at  52.8° 

20° 
d  —  0.6949,  nD  1.3866.    It  is  easily  dissolved  by  nitric  acid  (1.52) 

and  reacts  with  concentrated  sulfuric  acid  giving  a  mixture  of  kero- 

»» Ber.  29,  2796  (1896). 

88  J.  Chem.  800.  75t  48   (1899). 

89  J.  Ruas.  Phys.-Chem.  Soc.  kk,  165   (1912* 


CYCLIC  NON-BENZEN01D  HYDROCARBONS  249 

sene-like  hydrocarbons  boiling  mostly  within  the  range  170°-360°. 
These  higher  boiling  hydrocarbons  are  probably  formed  by  the  inter- 
mediate formation  of  an  oleftne  followed  by  polymerization  in  accord- 
ance with  the  general  behavior  of  olefines  to  concentrated  sulfuric  acid 
which  has  been  discussed  elsewhere  in  these  pages.  With  nitric  acid  in 
glacial  acetic  acid  hydration  occurs,  resulting  chiefly  in  isopropyl  di- 
methyl carbinol.  It  is  reduced  by  Sabatier's  method  as  follows: 
CH3  CH.—  CH3  CH 


\  /I  I 

—  C  — 

CH 


3 
C   ....  -  >CH3CH2  —  C  —  CH3 

CH 

Fuming  hydroiodic  acid  and  bromine  break  the  cyclopropane  ring. 

Methylisopropylcyclopropane  is  formed  by  heating  methyl  iso- 
propyl pyrazoline  (from  isobutylidene-  acetone  and  hydrazine  hydrate) 
to  230°  with  caustic  potash.40 

CH3  CH3 

>CH  —  CH.NH.N        -  >        >CH  —  CH 
CH3  I  M  CH3  i     \ 

CH2  -  C-CH3  \ 

CH2  —  CH.CH3 

20°  20° 

The  hydrocarbon  boils  at  80°-81°,  d-^  0.7120,  n  -^-  1.3927. 

l-Methyl-1.2.-Diethylcyclopropane  has  been  made  by  Kishner's 

20° 
hydrazine  method.    It  boils  at  108°-109°,  d  —  0.7382,  nD  1.4102.    It 

is  markedly  more  stable  to  permanganate  solution  than  1.1.2.-tri- 
methylcyclopropane  and  is  also  less  reactive  to  bromine.41 

Methylisobutylcydopropane  was  made  by  Zelinsky  42  by  hydrogen- 
ating.  the  dimethylbicyclohexane,  shown  below,  in  the  presence  of 
platinum  or  palladium  black, 

CH, 
CH  —  CH2  CH  —  CH2CH  < 


CH2 


/ 

2 


^^f  -I~O.  ^^/  AJ.  O  ^-^  -1"1-  ^X» 

\       CH3  /\  CH3 


C< 


CH 


CH  — CH2     "<!  CH.CH, 

20° 


It  boils  at  110°-111°,  d—  0.7403.    In  the  presence  of  nickel  and  hy- 
drogen the  cyclopropane  ring  is  also  broken  and  reduced. 

*°Kishner,  J.  Russ.  Phys.-Chem.  Soc.  45,  987   (1913). 
41  Kishner,  J.  Russ.  Phys.-Chem.  Soc.  M,  165  (1912). 
**«/.  Russ.  tf,  831   (1913). 


250       CHEMISTRY  OF  THE  NON-MNZENOW  HYDROCARBONS 

l.l.-Dimethyl-2-Isobutenylcyclopropane  is  formed  when  phorone 
is  heated  with  hydrazine  hydrate;  boiling-point  132°,  d  •  0-  0.7677,  n 

1.442.43  It  may  be  oxidized  to  1  .  1  .  -dimethylcyclopropanecarboxylic 
acid  by  means  of  permanganate  without  rupture  of  the  ring.  Treat- 
ment with  fuming  HBr  gives  first  the  monobromide  and  then  the  di- 
bromide, 

CH3 
CH3  CH-CH  =  C<  CH3 

>C<|  CH3    CH3          CH  —  CH2  —  C< 

CH3          CH2  -  >         >C<|  I     CH, 

CH3  CH2  Br 

CH3  CH3 

-  >  >  CH  .  CH2CHBrCH2  —  C  < 

CH3  |      CH3 

Br 

A  tricarboxylic  acid  derivative  of  methyl  dicyclobutane  has  been 
prepared  by  Beesley  and  Thorpe44  and  is  mentioned  because  of  its 
curious  structure,  -its  method  of  preparation  and  the  fact  that 
it  exists  in  three  distinct  modifications,  in  accord  with  accepted 
ideas  of  stereochemistry.  When  the  dibromoethyl  ester  of  the  acid 
CH3C.  (CH2C02H)3  is  treated  with  pyridine  a  dilactone  ester  is  formed 
which  readily  yields  the  free  acid, 

CHBr.C02C2H5  CH.C02H. 

CH3C  —  CHBr  .  C02C2H5  --  >  CH3  —  C  —  C  .  C02H. 

XCH2C02C2H5  ^CH.CO.H. 

Three  distinct  modifications  melting  at  193°,  165°  and  154°  were  iso- 
lated, which  evidently  correspond  to  the  three  theoretically  possible 
acids, 

CH 


6 


\ 


\ 


\, 


c  -  c  -  -c 


C02H.  C02H        H     C02H      H  H  COJ 

48Kishner,  J.  Russ.  Phys.-Chcm.  Soc.  45.  957   (1913). 
44  J.  Chem.  Soc.  117  3  601  (1920). 


CYCLIC  NON-BENZENOID  HYDROCARBONS  251 

CH3 


c c 


/\          C02H    /       \ 
C02H      H  C02H        H 

These  acids  are  remarkably  stable  and  are  not  affected  by  prolonged 
boiling  with  aqueous  acids  or  alkalies. 

Cydobutane:  This  hydrocarbon,  boiling-point  11°-12°,  D4° 
0.7038,  is  readily  made  by  hydrogenating  cyclobutene  in  the  presence 
of  nickel  at  100°.  Hydrogen  in  the  presence  of  nickel,  at  180°,  con- 
verts cyclobutane  to  normal  butane.  It  is  stable  at  ordinary  tempera- 
tures to  bromine  and  hydriodic  acid.  Its  simple  derivatives  show  a 
striking  resemblance  in  physical  and  chemical  properties  to  the  deriva- 

CH2  — CHOH 
tives  of  n. butane.    Thus  cyclobutanol     I  and  n. butyl 

CH2  —  CH2 

alcohol  are  very  similar  in  odor  and  boiling-point,  123°  and  116.8°  re- 
spectively. W.  H.  Perkin,  Jr.,45  who  prepared  cyclobutanol,  stated,  "It 
shows  the  closest  resemblance  to  the  fatty  alcohols  containing  the  same 
number  of  carbon  atoms;  it  might,  indeed,  be  readily  mistaken  for  nor- 
mal butyl  alcohol."  Perkin  also  found  that  cyclobutylcarboxylic  acid 
behaves  very  much  like  valeric  acid,  the  amide  giving  excellent  yields 
of  the  amine,  with  bromine  and  caustic  potash. 

CH2  —  CH .  CONH2  CH2  —  CHNH2 

CH2  —  CH2  CH2  —  CH2 

The  cyclobutane  derivatives  all  have  slightly  higher  boiling-points 
than  the  corresponding  normal  butane  derivatives. 

Cyclobutyl  Series  Normal  Butyl 

Substance  B.-P.  Substance  B.-P.  Difl. 

R.CO,H  195°  RxCOiH  186°  9* 

R.NH,  81°  RxNH,  76°  5° 

R.OH  123°  RiOH  116°  7° 

R.C1  85°  RxCl  77°  8° 

RBr  104°  RiBr  100°  4° 

RI  138°  RJ  131°  7* 

48  J.  Chem.  800.  65,  950  (1894). 


252       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

Willstatter 46  and  his  co-workers  have  applied  the  well-known  method 
of  exhaustive  methylation  and  decomposition  of  the  tertiary  base,  to 
the  preparation  of  cyclobutene. 

CH3 

CH2 CH  — NH2  CH2 CH  — N  — CH3 

OH  CH3 
CH CH2  CH2 CH2 

CH2  —  CH 

I  ||       +N(CH3)3  +  H20 

CH2  —  CH 

Cyclobutene  readily  adds  one  molecule  of  bromine  to  form  the  com- 
paratively stable  dibromide  boiling-point  171°-174°.  When  heated 
with  quinoline  this  dibromide  decomposes  with  rupture  of  the  ring,  giv- 
ing butadiene  but  with  caustic  potash  at  200°  acetylene  is  formed.47 

=  CH  1  HC  ==  CH 

CH2  — CHBr         /i     +  (KOH) 


FCH  = 
| 

|_CH  = 


CH2  —  CHBr         \  +  quinoline  -  -*  CH2  =  CH  -  -  CH  =  CH2 

The  following  methods  of  rupturing  the  ring  of  cyclobutane  or  its 
simple  derivatives  have  been  observed. 

(1)  CH2  — CH2 

| »  H2  +  Ni  at  180° >  CH3CH2CH2CH3 

CH2  —  CH2 

(2)  CH2  —  CHC02.iCa  +  Ca(OH)2 

CH2  —  CH2  >  2CH2  =  CH2  +  CaC03 .  +  H20 

heat 

(3)  1 . 2-dibromocy  clobutane  +  quinoline  >  butadiene. 

(4)  Cyclobutylamine  phosphate  +   heat  >  butadiene. 

(5)  1.2-dibromocyclobutane   +   KOH     —     >      acetylene. 

Gustavson  48  prepared  a  hydrocarbon  C5H8  by  the  action  of  zinc  in 
alcohol  on  C(CH2Br)4  and  from  the  manner  of  its  formation  and  its 
physical  properties  and  chemical  behavior  Gustavson's  hydrocarbon 
has  been  considered  to  be  spirocyclane, 

*"  B&r.  38,  1992    (1905)  ;  40.  3979    (1907). 

47  The  1.3-diphenyl  derivative  of  cyclobutadiene  is  a  stable  crystalline  hydrocarbon 
melting  at  130°.     [Gastaldi  &  Cherchi,  Ooze.  chim.  Ital.  M   (1),  282.] 

48  J.  prakt.  Chem.   (2)   5^  105    (1896)  ;  56,  93   (1897). 


CYCLIC  NON-BENZENOID  HYDROCARBONS  253 

BrCH2  CH2Br  CH2  CH, 

\   / 

C  > 

BrCH2  CH2Br 

However,  it  has  been  shown  that  by  careful  fractional  distillation  Gus- 
tavson's  product  may  be  separated  into  two  hydrocarbons,  one  boiling 
at  37.5°  and  the  other  at  42°.  Philipow 49  has  demonstrated  that  both 
hydrocarbons  are  derivatives  of  cyclobutane,  the  lower  boiling  one 
yielding  levulinic  acid  on  oxidation, 

CH3 
CH2  —  C  —  CH3          CH2  —  C  <  CH2  —  CO  —  CH3 


>  OH   > 

CH2-CH 

CH0  —  CH.OH.          CH 


2  — C02H 


methylcyclobutene 


The  hydrocarbon  boiling  at  42°  proved  to  be  methenecyclobutane. 
Both  hydrocarbons  yield  the  same  hydroiodide  and  treatment  of  this 
iodide  with  moist  silver  oxide  yields  an  alcohol  boiling  at  116°-119°. 
The  same  alcohol  is  obtained  directly  from  both  hydrocarbons  by 
careful  hydration  by  dilute  sulfuric  acid, 

CH3 

CH2  —  C  —  CH3  CH2  — C< 

+  HI      I  II 


H2  —  CH  CH2  —  CH2      \ 

\  \  CH3 

CH2  —  C  —  CH2      \        /^  CH,  —  C<T 

I  \/  OH. 

H2  —  CH2  \j    >          CH2  —  CH2 

dil.  H2S02 

Previous  results  on  the  oxidation  of  the  hydrocarbon  boiling  at  42°  and 
the  alcohol  had  led  to  no  very  definite  results,  but  Philipow  showed 
that  the  oxidation  of  the  alcohol  is  strictly  analogous  to  the  oxidation 
of  1  -methy  Icy  clohexanol  ( 1 ) , 

49  J,  prakt.  Chem.  (2)  93,  162  (1916). 


254       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

CH2C02H      principal 
CH3C02H  +  CH2< 
/  CH2C02H      reaction 


\ 

\ 

HC02H  +  cyclohexanone. 

CH3 

CH2  —  C<  C02H    C02H    principal 

OH.       /  CH3C02H  +  CH2<     —  >  | 

/  C02H  CO2H    reaction 

CH2  —  CH2          \ 

\  HCOoH  +  CH2  —  CO          CH2  —  C02H 


CH, 


CH2         CH2  — C02H 


Hydrogenation  had  yielded  a  hydrocarbon  C5H10,  supposed,  on  the 
basis  of  the  spirocyclane  structure,  to  be  ethylcyclopropane.  Philipow 
made  ethylcyclopropane 50  by  Kishner's  admirable  method,  from 
acetylcyclopropane, 

CH2  CH2 

I      >CH.CO.CH3  +  H2N.NH2  ->  I      >CH.CH2CH3  +  N2  +  H2O 
CH2  CH2 

Perkin  and  Colman51  had  stated  that  methylcyclobutane  was  pro- 
duced by  the  action  of  sodium,  in  toluene,  on  1 . 4-dibromopentane  but 
on  repeating  their  work  Philipow  obtained  a  similar  product  but  showed 
that  it  was  a  mixture  of  hydrocarbons,  in  which  he  identified  piperylene 
and  n .  pentene.  Demj  anow  52  had  made  methylcyclobutane  by  the  ac- 
tion of  zinc  in  acetic  acid  on  cyclobutylmethyl  iodide.  Philipow  made 
this  hydrocarbon  in  two  ways,  from  cyclobutylaldehyde  C4H7.CHO 
by  Kishner's  method,  and  also  by  reduction  of  Gustavson's  hydrocar- 
bons by  colloidal  palladium  (Skita's  method),  and  the  hydrocarbon 
obtained  by  the  three  methods  proves  to  be  identical,  i.  e.,  methyl- 
cyclobutane, boiling-point  36° -36. 5°  (755mm.),d^3  0.7118,  MR  23.58, 

MR  calc.  23.02.  Methylcyclobutane  reacts  with  hydrogen  in  the  pres- 
ence of  catalytic  nickel  at  205°  to  give  isopentane. 

MPhilipow's   ethylcyclopropane  boils  at  36.5°    (755mm.),  d  "4^0.7055,   MR   23.61, 
MR  calculated  23.02. 

"«/.  Chem.  Soc.  53,  201   (1888). 

82  J.  Ruse.  Phya.-Chem.  Soc.  &,  842  (1910). 


CYCLIC  NON-BENZENOID  HYDROCARBONS  255 

18° 
Cyclobutanone,  boiling-point  99°-101°,  d-^^  0.9344,  has  an  odor 

lo 

resembling  acetone.  Oxidation  by  nitric  acid  yields  succinic  acid.  It 
was  made  by  Kishner  from  cyclobutanecarboxylic  acid  by  treating 
with  ammonia  to  form  the  amide,  brominating  and  then  treating  with 
bromine  and  caustic  potash, 

CH2  CH2 

CH2  CH .  C02H >  CH2  CHCONH2 > 

CH2  CH2 

CH2  CH2 

/       \  /       \ 

CH2  C  — CONH2          CH2  CO 

\       /I  — >        \        / 

CH2    Br  CH2 

Cyclobutene  is  of  interest  on  account  of  the  series  of  bromine 
substitution  products  which  can  be  prepared  from  it  without  rup- 
ture of  the  ring.  Thus  cyclobutene  adds  a  molecule  of  bromine  to 
form  1.2-dibromocyclobutane.  On  treating  this  with  alkali  one  mole- 
cule of  hydrogen  bromide  is  removed  and  the  resulting  bromocy- 
clobutene,  like  aliphatic  defines  containing  halogen,  is  relatively 
quite  stable.  It  adds  HBr  to  form  1 . 1-dibromocyclobutane  which 
on  hydrolyzing  with  aqueous  lead  oxide  yields  cyclobutanone. 
Bromocyclobutene  adds  bromine  to  form  1 . 1 . 2-tribromocyclobutane, 
which  can  be  converted  to  CH2  —  CBr  by  loss  of  HBr,  and  this  in 


AH.-!!. 


Br 
turn  adds  bromine  to  give    CH2  —  CBr2     melting-point  126°  and  this 

CH2  — CBr2 

can  be  further  brominated  without  breaking  the  ring  to  form  penta- 
bromocyclobutane,  and  hexabromocyclobutane  melting  at  186.5 °.53 

Ethylcyclobutane  has  been  prepared  by  a  very  roundabout  method 
from  the  amide  of  cyclobutanecarboxylic  acid,  which  was  converted 
into  cyclobutylmethyl  ketone,  this  reduced  to  cyclobutylmethylcar- 
binol  and  the  latter  converted  to  the  corresponding  iodide  and  reduced 
by  zinc  dust  and  acetic  acid.54  The  hydrocarbon  boils  at  72.2°-72.5°, 

83  Willstatter  &  Bruce,  Ber.  40,  3979   (1908) 
"Zelinsky  &  Gutt,  Ber.  84,  2432   (1908). 


256       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

1ft°  20°  19  5° 

0.7540,  d-      0.7450  and  n  --    1.4080.    Oxidation  by  nitric  acid 


yields  succinic  acid.  Cyclobutylmethyl  ketone  boils  at  136°-136.5° 
(semicarbazone  melting  at  148°)  and  the  cyclobutylmethylcarbinol 
C4H7.CHOH.CH3,  boils  at  144°  (phenylurethane  melting  at  87.5°- 
88°). 

Lebedev55  has  shown  that  when  substituted  allenes  are  polymer- 
ized, cyclobutane  derivatives  are  formed.  When  unsymmetrical  di- 
methyl allene  is  heated  in  sealed  tubes  the  principal  product  is  1  .2-di- 
isopropylidenecyclobutane  CH2  —  C  —  C  (CH3)  2  together  with  1  .  1- 

CH2  —  C  =  C(CH3)2 
dimethyl-2-methylene-3-isopropylidenecyclobutane.     The  former  hy- 

20°  1Q  7° 

drocarbon  boils  at  179°-181°,  d  —  0.8422,  n  ^-  1.5008  from  which 

the  increment  of  the  molecular  refraction  is  shown  to  be  2.32.  It  is 
readily  hydrogenated  to  1  .  2-diisopropyl-cyclobutane,  boiling  at  157°- 

0° 
158.5°,  d  _  0.7901.    The  monoozonide  yields  isopropylidene-2-cyclo- 

butanone,   CH2  —  C  =  0  boiling-point    171°.     Isopropyl-2- 

CH2  —  C  =  C(CH3)2 

cyclobutanone  obtained  by  reduction,  boils  at  148°-150°  (semicarba- 
zone melting  at  183°). 

The  hydrocarbon  1  .l-dimethyl-8-methylene-8-isopropylidene  boils 

20° 
at  149°-150°,  d  —0.7982.    The  corresponding  saturated  hydrocarbon 

obtained  by  reduction,  i.  e.,  —  1  .  1  .  2-tTimethy\-3-isopropylcyclobutane, 

20° 
boils  at  145°-146°,  d  —  0.7598.    The  two  unsaturated  hydrocarbons 

have  a  sharp  kerosene-like  odor.  The  two  saturated  hydrocarbons  are 
not  attacked  by  aqueous  permanganate.  The  stability  of  the  satu- 
rated cyclobutanes  to  sulfuric  acid  has  not  been  noted. 

Cyclobutane-1  .1-Dicarboxylic  Acid,  melting-point  155°,  is  pre- 
pared by  a  general  method  discovered  by  Perkin,  i.  e.,  —  the  reaction 
of  1  .  3-dibromopropane  and  sodium  malonic  acid  ester  or  sodium  cyan- 
acetic  ester. 

CH2Br  C02R  CH2  C02H 

CH2<  +  2Na  +  H2C<  -  >CH2<         >C< 

CH2Br  CN  CH2  C02H 

Decomposition  of  the  dicarboxylic  acid  yields, 

86  J.  Ruse.  Phys.-Chem.  Soc.  48,  820   (1911). 


CYCLIC  NON-BENZEN01D  HYDROCARBONS  257 

Cyclobutanecarboxylic  Acid,  boiling-point  194°.  The  acids  of  this 
type  resemble  fatty  acids  very  closely,  this  acid  readily  yielding  a 
pleasant  smelling  ethyl  ester  boiling  at  160°,  an  anhydride  boiling  at 
160°,  an  amide  melting  at  130°  and  a  nitrile  boiling  at  150°.  Hydri- 
odic  acid  at  200°  breaks  the  ring  forming  n. valeric  acid.56  When  the 
silver  salt  is  treated  with  iodine,  a  peculiar  condensation  with  forma- 
tion of  the  ester  of  cyclobutanol  results,57 

2C4H7C02Ag  +  I2  -    ->  C4H7C02 .  C4H7  +  C02  +  2AgI 

Cyclobutane  1 .1 .2.2.-Tetracarboxylic  Acid,  melting-point  145°- 
150°  is  formed  by  the  reaction 

C02R  C02R 

CH2  — CNa<  CH2— C< 

C02R  I     C02R 

Br2 

C02R  — >                     C02R 

2  — CNa<  or  I2          CH2— C< 

C02R  C02R 

On  heating  the  free  acid  it  loses  two  molecules  of  carbon  dioxide  and 
forms  cyclobutane-l-2-dicarboxylic  acid,  melting  at  137°,  known  in  cis 
and  trans  forms.  On  brominating  the  1 . 2-dibromide  is  formed.  By 
the  action  of  caustic  alkalies  one  molecule  of  HBr  is  removed  to  form 
the  bromocyclobutene  carboxylic  acid, 

CH2  —  CBr  —  C02H .  CH2  —  CBr 

KOH  +  C02  +  HBr 


H2  —  CBr  —  C02H .  CH2  —  C .  C02H 

Silver  oxide  in  water  replaces  both  bromine  atoms  with  hydroxyl,  these 
reactions  being  quite  analogous  to  the  formation  of  bromofumaric  acid 
and  tartaric  acid  from  isodibromosuccinic  acid  under  the  same  condi- 
tions, 

CHBr.C02H.  CH  — C02H  CH(OH).C02H 

>     M  and       | 

CHBr .  C02H  CBr— C02H  CH  (OH) .  C02H . 

Cyclobutane  -1 .8-Dicarboxylic  Acid  is  known  in  cis  and  trans 
forms,  melting  at  136°  and  171°,  respectively.  Simonsen  5S  has  shown 
that  when  the  ethyl  ester  of  p-methoxymethylmalonic  acid  is  digested 

"Kishner,  J.  Russ.  Phys.-Chem.  Soc.  40,  673  (1908). 
"Demjanov,  J.  Russ.  Phys.-Chem.  Soc.  JkS,  835  (1911). 
•J.  Chem.  Soc.  93,  1778   (1908). 


258       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

with  hydrochloric  acid  it  yields  cis-cyclobutane-1.3-dicarboxylic  acid. 

The  cyclobutane  ring  exists  in  a-truxillic  acid,  which,  according 
to  De  Jong,59  is  1.3-diphenyl-cyclobutane-2.4-dicarboxylic  acid.  It  is 
formed  from  cinnamic  acid  by  the  action  of  light  and  on  heating  breaks 
up  again  into  cinnamic  acid. 

Cydopentane:  The  relationship  between  cyclopentane  and  cyclo- 
hexane,  or  their  derivatives,  is  exceedingly  close,  and  the  increasing 
number  of  instances  known,  in  which  change  of  the  one  ring  system 
into  the  other  occurs,  makes  evident  the  rationality  and  convenience 
of  considering  these  two  ring  systems  together,  rather  than  isolating 
the  cyclohexane  derivatives  as  "hydroaromatic"  compounds,  as  has 
usually  been  done  heretofore  and  thus  widely  separating  the  subject 
matter  dealing  with  these  two  ring  systems.  Examples  of  the  con- 
version of  these  two  ring  systems,  one  into  the  other,  have  been  noted 
in  the  section  on  Rearrangements.  Thus  one  of  the  smoothest  reactions 
of  this  kind  is  the  nearly  quantitative  conversion  of  1  -methyl- 1  -a-hy- 
droxyethylcyclopentane  to  l^-dimethyl-A^cyclohexene  by  zinc  chlo- 
ride.60 Cyclopentane  is  also  formed  when  the  bromide  of  cyclobutyl- 
carbinol  is  reduced  by  the  zinc-palladium  couple  and  hydrobromic 
acid.61  Kishner  showed  that  when  benzene  is  reduced  under  high  pres- 
sure at  280°,  according  to  Wreden,  that  the  product  is  not  cyclohexane 
but  methylcyclopentane 62  and  Markownikow 63  has  shown  several  in- 
stances in  which  benzene  hydrocarbons  give  cyclopentane  derivatives 
on  hydrogenation.  Cyclohexanol  yields  chiefly  methylcyclopentane  on 
heating  with  concentrated  hydriodic  acid.  The  hydrocarbons  them- 
selves are  quite  stable;  only  in  reactions  of  their  derivatives  does  re- 
arrangement of  the  ring  structure  occur  easily.  Thus  Markownikow 
and  Fortey  64  independently  observed  that  cyclohexane  could  be  heated 
with  hydriodic  acid  (and  red  phosphorus)  in  sealed  tubes  to  240°  with- 
out change.  Methylcyclohexane  is,  however,  partially  rearranged  by 
heating  with  hydriodic  acid  to  270°  to  dimethylcyclopentane,  and  this 
change  is  effected  without  the  formation  of  higher  boiling  products,  in 
other  words,  is  not  a  thoroughgoing  decomposition  such  as  occurs  in 
"cracking"  processes.  Methylcyclopentane  is  one  of  the  products  of 
the  action  of  aluminum  chloride  on  cyclohexane.65 

"Chem.  Abs.  1918,  1385;  Stoermer  &  Laage,  Ber.  54,  77   (1921). 

«°Meerwein,  Ann.  417,  255    (1918). 

«Demjanow,  Ber.  40,  4960   (1907). 

62  J.  Rues.  Phys.-Chem.  Soc.  29,  210   (1897). 

M  Ber.  SO,  1214  (1897). 

"Proc.  Ghem.  Soc.  1897,  161. 

•'Aschau,  Ann.  32J,  12   (1902). 


CYCLIC  NON-BENZENOID  HYDROCARBONS  259 

Cyclopentane  was  prepared  by  Wislicenus  66  from  cyclopentanone, 
the  latter  being  prepared  by  the  well-known  method  of  heating  calcium 
adipate.  Cyclopentanone  is  also  a  constituent  of  the  oily  residues  re- 
covered in  the  rectification  of  wood  alcohol.  The  ketone  on  reduction 
under  the  same  conditions  usually  applied  to  ordinary  aliphatic  ke- 
tones,  for  example,  reduction  by  means  of  sodium  in  moist  ether,  yields 
cyclopentanol.  The  alcohol  has  an  odor  resembling  amyl  alcohol,  boils 

21  5° 

at  139°,  d  '  0.9395.  Cyclopentanol  is  converted  into  the  corre- 
sponding iodide  by  saturating  with  hydrogen  iodide  and  hydrogen  bro- 
mide yields  the  bromide,  without  rupture  of  the  ring.  Reduction  of 
the  iodide  under  the  usual  conditions,  zinc  and  hydrochloric  acid  in 

20  5° 

dilute  alcohol,  yields  cydopentane,  boiling-point  50.5°-50.7°,  d      ' 

0.7506. 

Cyclopentane  is  inert  to  bromine  in  the  dark  but  in  sunlight  sub- 
stitution with  evolution  of  HBr  occurs,  approximately  with  the  same 
ease  as  in  the  case  of  normal  pentane.  On  heating  with  bromine  in  a 
sealed  tube  the  reaction  is  very  slow  at  100°  but  more  rapid  at  128°- 
130°,  the  reaction  then  being  accompanied  by  deposition  of  carbon. 

Cyclopentane  has  not  been  sulfonated,  the  hydrocarbon  being  quite 
stable  to  sulfuric  acid.  Borsche  6r  has  prepared  Cyclopentane  sulfonic 
acid  by  an  indirect  method  involving  the  conversion  of  cyclopentanol 
to  the  bromide,  reacting  on  the  bromide  with  magnesium  in  ether  and 
treating  the  magnesium  complex  C5H9MgBr  with  S02  and  then  oxidiz- 
ing with  aqueous  permanganate.  The  potassium  cyclopentyl  sulfonate 
was  crystallized  from  absolute  alcohol.  Salts  of  methylcyclohexane-3- 
sulfonate  were  prepared  in  the  same  manner  from  1  methyl-3-bromo- 
cyclohexane. 

Cyclopentene  is  readily  formed  on  warming  cyclopentyl  iodide  with 
alcoholic  caustic  potash,  closely  resembling  amyl  iodide  and  its  con- 
version to  amylene  under  the  same  conditions.  Cyclopentene  boils 
at  46°.  When  cyclopentyl  bromide  is  employed  a  small  proportion  of 
cyclopentyl  ethyl  ether  is  also  formed,  again  paralleling  the  n.amyl 
derivatives.  From  Cyclopentene  Meiser 68  prepared  the  dibromide, 
which  he  converted  to  the  1 . 2-gly col  by  hydroly zing  with  aqueous  po- 
tassium carbonate;  the  glycol  was  converted  to  the  chlorohydrin  by 

"Ann.  275,  327   (1893). 

87  Ber.  W,  2220  (1907).  Borsche  prepared  l-niethyl-cyclohexane-3-sulfone-chloride, 
which  on  reduction  yields  the  1-methyl  cyclohexane-thiol  (3),  boiling  at  172°, — the 
first  of  the  cyclic  mercaptans  to  be  synthesized. 

MBer.  S2,  2050   (1899). 


260       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

hydrochloric  acid  and  the  same  product  was  made  by  the  addition  of 
hypochlorous  acid  to  cyclopentene. 

In  the  cyclopentane  series  a  very  large  number  of  derivatives  are 
known,  but  the  great  majority  of  them  have  been  synthesized  by 
costly  and  usually  very  roundabout  methods.  The  hydrocarbons  them- 
selves have 'seldom  been  used  for  preparing  derivatives;  in  fact,  the 
hydrocarbons  have  been  prepared  from  the  derivatives.  Cyclopentane 
or  its  alkyl  derivatives  have  never  been  isolated  in  a  pure  state  from 
petroleum  or  any  other  natural  product. 

Cyclopentadiene,  boiling-point  41°,  may  be  isolated  from  the  fore- 
runnings  when  crude  benzene  is  distilled,69  and  Etard  and  Lambert 70 
found  it  among  the  products  of  the  thermal  decomposition  of  heavy 
paraffine  oil.  It  polymerizes  spontaneously  to  the  dimeride  C10H12  on 
standing  at  ordinary  temperatures  and  on  distillation  the  dimeride  is 
partially  inverted  to  the  original  hydrocarbon.  The  dimeride  (un- 
known constitution)  boils  at  170°.-  Stobbe71  finds  that  the  spon- 
taneous conversion  to  the  dimeride  is  complete  in  about  30  days  and 
when  exposed  to  oxygen  or  air  a  diperoxide  of  the  dimeride  is  formed, 
which  Stobbe  regards  as  having  the  following  structure,  • 


0 


/ 


CH  — CH  — CH  — CH 


\ 


0 


CH      CH  — CH      CH 

\/  \/ 

CH2  CH2 

The  dimeride  is  much  more  stable  than  the  original  hydrocarbon 
but  may  be  further  polymerized  by  heating  to  160°-180°  in  a  sealed 
tube,  a  solid  resin  being  formed.72  The  polymers  of  acyclic  olefines 
and  dienes  are  also  more  stable  than  the  original  hydrocarbons,  the 
difference  being  marked  in  their  behavior  to  concentrated  sulfuric  acid, 
hydrogen  chloride,  hydrogen  bromide,  etc.  Hydrogen  chloride  com- 
bines with  cyclopentadiene  to  form  a  monochlorocyclopentene,  boiling- 
point  50°  (40mm.),  and  this  derivative,  though  not  further  acted 
upon  by  hydrogen  chloride,  combines  readily  with  chlorine  to  form  a 
trichlorocyclopentane  boiling  at  196°.  Addition  of  bromine  to  cyclo- 
pentadiene gives  two  stereoisomeric  1.4-dibromides,  one  a  liquid  and 

"Kraemer  &  Spilker,  Ber.  29,  552    (1896). 
™Compt.  rend.  112,  945   (1891). 
71  Ber.  52,  1436   (1919). 
"Kronstein,  Ber.  35,  4150  (1902). 


CYCLIC  NON-BENZEN01D  HYDROCARBONS  261 

one  a  crystalline  solid  ;  the  dibromides  yield  two  stereo-isomeric  aa-di- 
bromoglutaric  acids  on  oxidation.  Cyclopentadiene,  like  isoprene,  com- 
bines with  quinones  to  give  stable  crystalline  compounds  ;  for  example, 
with  benzoquinone  to  form  the  product  C^H^C^,  melting-point  78°. 
Cyclopentadiene  reacts  violently  with  concentrated  sulfuric  acid  and 
dilute  sulfuric  acid  resinifies  it.  Like  cyclohexadiene,  its  polymers  do 
not  resemble  caoutchouc  but  are  resinous. 

Cyclopentadiene  is  of  special  interest  on  account  of  the  reactivity 
of  the  CH2  group.  The  hydrocarbon  reacts  with  potassium  with  evolu- 
tion of  hydrogen,  forms  C5H5MgI  from  CH3MgI  with  evolution  of  me- 
thane 73  and  readily  condenses  with  aldehydes  and  ketones  under  the 
influence  of  sodium  ethylate.  Thiele  7*  attributes  this  reactivity  to  the 
unsaturated  character  of  the  contiguous  groups,  its  condensation  with 
aldehydes  and  ketones  paralleling  the  reactivity  of  substances  contain- 
ing the  group  0  =  C  —  CH2  —  C  =  O  with  these  reagents  under  the 
same  conditions.  With  acetone,  acetophenone,  and  benzophenone  the 
following  intensely  colored  hydrocarbons  are  formed: 

CH  =  CH  CH3 

>  C  =  C  <  dimethy  Ifulvene 

CH  =  CH  CH3 

CH  :=  CH  CH3 

>C  =  C<  methylpheny  Ifulvene 

CH  =  CH  C6H5 

CH  =  CH  C6H5 


dipheny  Ifulvene 
CH  =  CH  C6H5 

Courtot  75  has  pointed  out  the  similarity  in  chemical  behavior  of  the 
CH2  in  Cyclopentadiene  with  the  corresponding  group  in  fluorene  and 
indene,  which  hydrocarbons  are  also  colored.  The  fulvene  derivatives, 
discovered  by  Thiele,  polymerize  on  warming  and  absorb  oxygen,  by 
autoxidation  much  more  rapidly  than  Cyclopentadiene.76  Stobbe  and 
Diinnhaupt77  have  shown  that  Cyclopentadiene  polymerizes  very  slowly 
in  the  absence  of  oxygen  and,  unlike  styrol,  the  polymerization  is  but 
very  slightly  affected  by  light. 

4-Methyl-2-Ethylcyclopentadiene:    When  the  ethyl  ester  of  levu- 

»  Grignard  &  Courtot,  Compt.  rend.  158,  1763  (1914)  ;  Courtot.  Ann.  chim.  \,  5> 
(1915)  . 

™Ber.  S3,  666  (1900)  ;  54,  68  (1901). 

"Loc.  cit. 

"Engler  &  Frankenstein,  Ber.  84,  2933   (1901). 

"  Ber.  52,  1436  (1919). 


262       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

linic  acid  in  alcohol  solution  is  condensed  by  sodium  ethylate,  an  un- 
saturated  cyclic  dicarboxylic  ester  is  formed  which  may  have  either 
of  the  two  following  structures, 

I.        CH3  —  C  —  CH2  —  C  —  C02H 

CH  -        -  C  —  CH2CH2 .  C02H 

4-methylcydopentadiene-l-carboxy-£-propionic  acid 

II.        CH3  —  C  —  CH2  —  C  —  C02R 

R02C  —  CH2  —  C C  —  CH3 

2 . 4-dimethylcyclopentadiene-l -carboxy-3-acetic  acid 

The  discoverers  of  the  condensation  of  levulinic  ester  favor  I  as  being 
the  structure  of  the  reaction  product.  The  free  acid  melts  at  218°,  with 
evolution  of  carbon  dioxide  and  formation  of  the  hydrocarbon,  the 
structure  of  which,  if  the  above  structure  I  proves  to  be  correct,  is 
4-methyl-2-ethylcyclopentadiene.  The  hydrocarbon  boils  at  135°,  but 
on  distilling  at  ordinary  pressure  about  one-third  is  polymerized,  the 
tendency  to  polymerize  evidently  being  abnormally  great.78 

Methylcyclopentane  has  been  made  synthetically  by  a  number  of 
methods  and  has  been  shown  to  be  present  in  the  light  distillate  from 
Russian  petroleum.  Methyl-cyclopentane-2-one  is  formed  by  heating 
the  calcium  salt  of  p-methyladipic  acid.  The  ketone,  boiling-point 
143.5°,  may  be  purified  by  the  sodium  bisulfite  compound,  then 
reduced  to  methylcyclopentanol- (2) ,  boiling-point  150.5°-151°,  and 
the  latter  reduced,  by  heating  with  concentrated  hydriodic  acid,  to 
methylcyclopentane.80  When  made  by  reducing  the  iodide,  l-methyl-2- 
iodo-cyclopentane,  by  the  copper  zinc  couple  the  hydrocarbon  showed 

0° 

the  following  physical  properties,81  boiling-point  71°-72°,  d—  0.7664. 

It  has  an  odor  like  well-refined  gasoline.  A  mixture  of  concentrated 
sulfuric  and  nitric  acid  has  little  effect  on  it  but  fuming  nitric  acid 
alone  reacts  rather  violently,  acetic  acid,  carbon  dioxide  and  water 
being  the  chief  reaction  products.  Nitric  acid  Sp.  Gr.  1.075,  at  115°- 
120°  gives  chiefly  the  tertiary  nitro  derivative.  According  to  Namet- 
kin,82  2-nitro-l-methylcyclopentane  is  also  formed,  boiling-point  98°- 

22° 
99°  at  40  mm.,  d  -JQ-  1.0381,  and  succinic  and  a-methylglutaric  acids 

"Duden  &  Freydag,  Ber.  S6,  944  (1903). 

80  Konowalow,  J.  Russ.  Phya.-Chem.  Soc.  £8,  125. 

81  Markownikow,  Ber.  SO,  1222   (1897). 

nJ.  Ruas.  Phya.-Chem.  Soc.  43,  1603   (1911). 


CYCLIC  NON-BENZENOID  HYDROCARBONS  263 

are  also  formed.  The  tertiary  nitro  derivative  can  be  isolated  from  the 
secondary  nitro  derivatives  by  dissolving  the  latter  in  aqueous  alkali. 
According  to  Markownikow 83  tertiary  nitromethylcyclopentane  boils 
at  92°  (40  mm.)  or  at  177°  at  atmospheric  pressure,  with  considerable 
decomposition.  Both  nitro  derivatives  give  good  yields  of  the  corre- 
sponding amines  when  reduced  by  tin  and  hydrochloric  acid.  The 
tertiary  amine  may  be  converted  into  the  corresponding  tertiary  alco- 
hol by  nitrous  acid  and  after  distilling,  boiling-point  135°-136°,  solidi- 
fies to  crystals  melting  at  30°. 

Chlorine  reacts  energetically  with  methylcyclopentane  at  ordinary 
temperatures  in  diffused  daylight.84  The  tertiary  chloride,  prepared 
from  the  tertiary  alcohol,  is  unstable,  partially  decomposing  on  distil- 
lation, boiling-point  123°.  By  direct  chlorination  of  methylcyclopen- 
tane, derived  from  petroleum,  Markownikow  obtained  a  mixture  of 
chlorides  from  which  he  was  unable  to  isolate  any  definite  product, 
the  presence  of  cyclohexane  in  the  original  methylcyclopentane  adding 
to  the  difficulty. 

Methylcyclopentane  has  been  made  by  means  of  the  Grignard  re- 
action, ring  closing  being  brought  about  by  treating  5-acetylbutyl- 
iodide  with  magnesium  in  ether, 


CH2  —  CH2  —  CO  —  CH3  CH2  —  CH2  CH3 

+Mg       |  >C< 

— CH2I  >   CH2  — CH2  OMgl 


CH0  — CH2  CH3 

I  >C< 

CH2  —  CH2          OH 

the  alcohol  being  converted 
into  the  iodide  and  the  latter  reduced  by  zinc  dust  and  acetic  acid.85 

Cyclopentanone.  This  ketone  has  usually  been  prepared  by  ring 
closing  of  the  ethyl  ester  of  adipic  acid  by  means  of  sodium.  The 
resulting  ester  may  be  regarded  as  a  carbocyclic  derivative  of  aceto- 
acetic  ester  and  by  the  general  method  of  decomposing  such  esters  to 
ketones,  this  cyclic  ester  yields  cyclopentanone, 

CH2  — CH2  — C02R        +Na        CH2  — CH C02R 

|  — »   I  >CO > 

CH2  —  CH2  —  C02R  CH2  —  CH2 

83  Ann.  307,  355  (1899). 

84  Markownikow,  loc.  cit. 

85Zelinsky  &  Moser,  Ber.  35,  2684   (1902). 


264       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

CH2  — CH2 

>        |  >CO. 

CH2  — CH2 

Thorpe  and  Best 88  have  described  a  series  of  derivatives  of  cyclo- 
pentanone  which  are  quite  stable  to  acids  but  are  decomposed  by  alkali 
with  rupture  of  the  ring,  the  ring  being  stable  to  acids  as  long  .as  a  CN 
or  C02C2H5  group  is  present  adjacent  to  the  ketone  group.  The  cor- 
responding imino  derivatives  are  exceedingly  stable  to  alkaline  hydro- 
lyzing  agents.  The  derivative  2-cyanocyclopentane-l-one  is  a  com- 
pound which  resembles  ethyl  cyanoacetate  in  many  of  its  properties; 
thus  when  treated  with  alcoholic  sodium  ethoxide  it  yields  a  sodium 
derivative  which  on  treating  with  methyl  iodide  yields  2-cyano-2- 
methyl-cyclopentane-1-one.  These  derivatives  will  not  be  described 
in  any  detail  but  are  mentioned  since  they  show  the  great  similarity  in 
the  chemistry  of  the  open  chain  and  cyclopentane  series,  and  also  since 
Best  and  Thorpe  showed  that  the  CN  group  could  readily  be  removed 
by  heating  with  dilute  sulfuric  acid  yielding  derivatives  of  cyclopen- 
tanone. 

CN  CN  CN 

CH2-  CH  CH2—  C .  Na  CH2—  C 


CO  +  NaOC2H5  CO     or 


H9—  CH, 


CONa 
/ 


H2—  CH2  CH2—  CH2  CH2-  CH 

CN 

+  RI    CH2  — C R  CH2  — CH 

\ 

CO      +  dil.  acid 

2  — CH2 

alkyl  cyclopentanones. 

Thorpe  and  Best  also  made  2.5-dimethylcyclopentane-l-one,  boiling- 
point  149°,  and  2-ethyl-cyclopentanone,  boiling-point  149°,  and 
2-methylcyclopentanone  by  similar  methods. 

Cyclopentanone  is  formed  during  the  carbonization  of  wood.     It 
boils  at  129°,  d20°  0.948,  n      1.4366.87     Acetic  anhydride  enolizes  it 

D 

MJ.  Chem.  Soc.  95,  690  (1909). 
•T  Wallach,  Ann.  353,  330. 


CYCLIC  NON-BENZENOID  HYDROCARBONS  265 

to  form  cyclopentenol  acetate.  The  semicarbazone  melts  at  205°-207° 
when  slowly  heated,  or  at  212°-213°  when  heated  rapidly.  It  con- 
denses with  formic  acid  ester  to  form  oxymethylenecyclopentanone 
C5H60  :  CH(OH),  melting-point  72°-73°.  A  cyclopentanonesulfonal 
is  known  melting  at  127°-128°. 

CH2  —  CH2 

\ 
C(S02C2H5)2 

CH2  —  CH2 

It  condenses  readily  with  aldehydes  to  form  derivatives  of  the  general 
type  88 

HC.R 

CH2  —  C 

CO 
2  —  C 

v, 

The  condensation  product  of  the  above  type  formed  with  benzaldehyde 
melts  at  191°,  with  anisaldehyde  215°,  cinnamic  aldehyde  222.5°,  pipe- 
ronal  257°  and  cuminol  145.5°.  Acetone  condenses  with  cyclopenta- 
none  89  to  form  the  isopropylidene  derivative, 

CH3 

CH2  —  C  =  C  ' 

CO      CH8 


a  liquid  very  soluble  in  water,  boiling  at  195°-199°.  Another  re- 
action which  has  been  useful  in  the  synthesis  of  hydrocarbons  derived 
from  cyclopentanone  is  the  condensation  with  bromoacetic  ester  and 
zinc,  according  to  Reformatsky's  method,  to  give  cyclopentanolacetic 
ester,  the  free  oxy  acid  decomposing  on  heating  to  give  methenecyclo- 
pentane,™  boiling-point  78°-81°. 

"Vorlander,  Ber.  89,  1838   (1896)  ;  Hobohm  &  Menzel,  Ber.  S6,  1499   (1903)  ;  Wal- 
lach,  Goett.  Nachr.  1907,  404. 
88  Wallach,  Ann.  894,  368. 
•°  Wallach,  Ann.  S47t  325. 


266      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


GEL—  CH 


CH2—  CH2  CH2  —  CH2  OH 

>CO >  |  >C< 

CH2  —  CH2  CH2C02H 

CH2—  CH2 

|  >C  =  CH2  +  H20  +  C02 

CR—  CR, 


Methenecyclopentane  has  a  penetrating  rather  disagreeable  odor, 
yields  the  glycol  C6H10(OH)2  on  oxidation  by  permanganate  and,  fol- 
lowing the  general  behavior  of  glycols,  this  glycol  is  converted  by  dilute 
acids  to  cyclopentane  aldehyde.  In  the  same  manner  a-bromopro- 
pionic  acid  yields  the  oxy  acid  from  which  ethylidenecyclopentane  may 
be  prepared.  This  hydrocarbon,  boiling-point  114°,  behaves  like  the 
terpenes  in  many  of  the  characteristic  reactions.  Thus  it  yields  a  ni- 
troso  chloride,  which  on  treating  with  alkali  loses  HC1  and  on  hydrolyz- 
ing  the  resulting  oxime,  A1-acetylcyclopentane,  is  formed,91 


CH2  —  CH2 


CH,  —  GIL 


CR,  — CR 


CR  —  CH. 


>C-C-CH8 

CH2  — CH2     | 


.OH 


CH2  — CH2 


CR  — CH 


C  —  C  —  CH3 


N.OH 


\ 


C  _  C  —  CH3 

II 
CH2  — CH  0 


Cyclopentanone  reacts  normally  with  the  Grignard  reagent,  giving 
l-methylcyclopentanol(l)  with  methyl-magnesium  iodide,92  or  the 
ethyl  derivative  with  ethyl-magnesium  iodide.93  These  tertiary  alco- 
hols readily  decompose  to  give  alkyl  cyclopentenes 


>C< 


OH 


CH2  —  CH2 

I 
CH  —  CH 


boiling-point  135° 
melting-point  35°-37' 


CR  — CH 


CH,  —  CR 


\ 

( 

/ 


C.CH, 


91  Wallach,  Ann.  365,  274. 

B2Zelinsky  &  Namjetkin,  Ber.  S5,  2683   (1902). 

M  Wallach,  Ann.  365,  276. 


CYCLIC  NON-BENZENOID  HYDROCARBONS 


267 


CH2  — CH2  OH 

I  >c< 

CH2  —  CH2          C2 


boiling-point  155°-157' 
d21.5°  0.916 


CH,—  CH 


\ 


C.C2H5 

CH2  — CH2 

boiling-point  108° 
d20°  0.7915 


By  condensing  with  bromoisobutyric  acid  and  decomposition  of  the  re- 
sulting oxy  acid,  isopropylidenecyclopentane  is  formed,  which,  like  ter- 
pinolene  and  other  hydrocarbons  having  a  semicyclic  double  bond  of 
this  nature,  is  converted  to  isopropylcyclopentene  by  alcoholic  sul- 
furic  acid,  the  double  bond  shifting  to  the  ring, 


CH9  —  CH, 


CH3 


\ 


CH2  — CH  CH3 

\-c/ 

/H2  — 


CH2  —  CH2  CH3 

boiling-point  136°-137° 
d20°  0.817 

The  reactivity  of  cyclopentanone  is  also  shown  by  its  condensation 
on  treating  with  sodium  ethylate  or  with  hydrogen  chloride  to  dicyclo- 
pentenepentanone,  which  may  be  reduced  first  by  hydrogen  and  palla- 
dium and  then  by  sodium  to  the  saturated  alcohol.  Heating  the  alco- 
hol with  zinc  chloride  yields  cyclopentylcyclopentene,  boiling-point 
197°-198°. 


CH— CH 


CH 


/u, 

>-CH<  «] 


CH, 


-CH, 


& 


H 


H. 


268      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

By  the  condensation  of  three  molecules  of  cyclopentanone  a  ketone 
C15H200  is  formed,  which  on  hydrogenation,  as  indicated  above,  yields 
the  saturated  ketone  dicyclopentylcyclopentanone,94  C15H200,  the  cor- 
responding alcohol  readily  yielding  dicyclopentylcyclopentene, 


!H2 

boiling-point  290°  at  760  mm.,  d20°  0.939 

This  hydrocarbon  may  be  regarded  as  a  tricyclic  "sesquiterpene." 

1 .2-Methylcyclopentanone 
CH8 


/         \ 

H2C  C  =  0        boiling-point  140°-141( 


H9C C 


d20°  0.917 
H, 


This  ketone  can  be  prepared  from  camphor-phorone,  or  from  a-methyl 
adipic  acid.  It  does  not  condense  with  aldehydes  in  the  presence  of 
caustic  soda. 

1  .S-Methylcyclop&ntanone,  boiling-point  144°-145°,  d22°  0.913,  can 
be  prepared  from  (3-methyladipic  acid.  It  condenses  readily  with  alde- 
hydes in  the  presence  of  caustic  soda,  the  benzaldehyde  compound 
melting  at  149°-151°  (inactive  form).  When  prepared  from  optically 
active  (3-methyladipic  the  1.3-methylcyclopentanone  is  also  active.95 
[a]  -f  124°-133°.  When  reduced  to  the  alcohol  and  then  converted 

D 

to  the  iodide,  the  latter  yields  l-methyl-A2-cyclopentene  when  treated 
with  alcoholic  caustic  potash.96 

"Wallach,  Ann.  389,  182. 

M  Wallach,  Ann.  SS2,  349  ;  S9L,  371. 

"Zelinsky,  Ber.  S5,  2488   (1902). 


CYCLIC  NON-BENZENOID  HYDROCARBONS 
CH, 


269 


HC 


H9C 


CH 


CH 


boiling-point  69 


0.7663 


a]D+  59.07 


l-methyl-A2-cyclopentene 

1 . 3-Methy Icy clopentanone  reacts  with  methyl-magnesium  iodide  to 
give  1.3-dimethylcyclopentanol(3),  boiling-point  143°-145°.  Accord- 
ing to  Zelinsky  this  tertiary  alcohol  is  decomposed  by  oxalic  acid 
mainly  to  l-methyl-3-methenecyclopentane,97 


CH3  — CH  —  CH2 


CH  — CH 


boiling-point  93 ( 

1Q° 
d--      0.7734 


Potassium     permanganate     solution     oxidizes     l-methyl-3-methene- 
cyclopentane  to  the  glycol  and  1 . 3-methylcyclopentanone. 

1. 3-Methy Icyclopentanone  condenses  with  acetone  98  to  form  4-iso- 
propylidene-l-methylcyclopentane-3-one,  which  can  be  employed  for 
the  synthesis  of  a  series  of  hydrocarbons  containing  the  methyl  and 
isopropyl  groups  in  the  1.4  position. 

CHS 

CH 
/   \ 


CH3 
CH 


>co  + 

CH,  H 


=  0  CH, 
CH, 


>C 


ii2C  CH2 

=  c — c  =  o 


"  Ber.  Sit,  3950  (1901). 
M  Wallach,  Ann.  394,  372. 


boiling-point  203°-205' 
d  — 0.9315 


270       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


The  ring  may  be  broken  by  the  rearrangement  of  the  oxime,  by  sul- 
furic  acid,  to  the  isoxime  and  hydrolyzing  the  latter  by  boiling  with 
hydrochloric  acid  to  amidocapronic  acid,"  a  reaction  which  is  very 
generally  applicable  to  the  cyclic  ketones. 

CH, 


H2C  CH2 


1 .1-Dimethylcyclopentane:  Kishner  10°  finds  that  all  of  the  re- 
actions of  dimethylcyclobutylcarbinol,  which  were  studied  by  him,  are 
abnormal  in  that  the  cyclobutane  ring  is  changed  to  the  cyclopentane 
ring.  The  carbinol  may  be  prepared  by  the  Grignard  reaction  ap- 
plied to  the  ester  of  cyclobutanecarboxylic  acid, 

CH2  +2CH3MgI  CH,  CH3 

CH2<        >CH.C02R >CH2<       ">CH  —  C< 

CH2  CH2  I      CH< 


AH 


When  this  carbinol  is  treated  with  hydrogen  bromide  the  product 
formed  is  2-bromo-l .  1-dimethylcyclopentane,  which  on  treating  with 
alcoholic  caustic  potash  yields  the  A2  unsaturated  hydrocarbon. 


CH2 

/        \  CH3 

CH2  CH  — C< 

o,lCH' 


HBr    CH2< 


CHBr 
CH9- 


CH8 
C< 

I     CH3 
CH9 


•»  Wallach,  Ann.  312,  184 

™J.  Rues.  Phys.-Chem.  Soc.  1,0,  994  (1908). 


CYCLIC  NON-BENZENOID  HYDROCARBONS  271 

CH, 

CH  —  C< 
//  I      CH3 

>        CH  boiling-point  78°-78.5° 

\  9O° 

CH2-6H2  dlF-    0.7580 

20° 
n  ^     1.4190 

It  has  an  odor  resembling  naphthalene.  On  oxidation  by  nitric 
acid  it  yields  aa-dimethylglutaric  acid.  According  to  Kishner,101  both 
hydrobromic  and  hydriodic  acids  reacting  on  the  above  carbinol  yield 
halogen  derivatives,  which  on  treating  with  alcoholic  caustic  potash 
yield  1.1.  -dimethy l-A2-cyclopentene  together  with  the  isomeric  hydro- 
carbon 1.2-dimethyl-A1-cyclopentene.  When  the  bromide,  obtained 
from  the  carbinol,  is  reduced  by  the  copper-zinc  couple,  a  saturated 
hydrocarbon  is  formed  which  Kishner 102  regards  as  1 . 1  Dimethylcy- 

20° 

clopentane,  boiling-point  88.3°-88.5°,  d  -^-  0.7553. 

1 .2-Dimethylcyclopentane,  obtained  by  reduction  of  1 . 2-dimethyl- 

90° 

A2-cyclopentene    by    Sabatier's    method,    boils    at    92.7°-93°,    d^ 

90° 
0.7534,  n^-   1.4126. 

1  .^-Dimethyl-^-Cyclopentene,  one  of  the  products  obtained  by 
the  decomposition  of  dimethylcyclobutylcarbinol,  as  described  above, 
is  identical  with  the  hydrocarbon  made  by  Maquenne103  from  per- 
seitol.  On  reduction  by  means  of  concentrated  hydriodic  acid  it  is 
converted  to  a  hydrocarbon  C-H17,  which  Aschan104  regarded  as  1.3- 
dimethylcyclopentane,  but  Kishner 105  states  that  more  probably  it  is 
1.2-dimethylcyclopentane  together  with  a  little  methylcyclohexane. 
The  olefine  reacts  with  hydrobromic  acid  to  form  an  unstable  bromide, 
yields  a  nitrosochloride  melting  at  73°-75°,  and  on  oxidation  yields 
y-acetobutyric  acid. 

CH2  —  C  —  CH3  CH2  —  COCH3 


CH, 


/ 

j 


CH 


/ 

\ 


CH2  —  C  —  CH,  CH9  —  CO,H 


3  vyxj.2 ^W2 


101  J.  Ruse.  PJiys.-CJiem.  Soc.  W,  994  (1908). 

102  J.  Russ.  Phys.-Chem.  Soc.  97,  509   (1905). 
108  J.  Chem.  Soc.  A&*.  1S9S   (1),  635. 

104  Chemie  d.  Alicyclischen  Verb,  p.  473. 

108  J.  Ruse.  Phys.-Chem.  Soc.  40,  994   (1908). 


272       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

1 .8-Dimethylcyclopentane  was  synthesized  in  an  optically  active 
form  by  Zelinksy106  from  d-1.3-dimethylcyclopentanol(3)  by  con- 
verting the  alcohol  to  the  iodide  and  reducing  the  latter  by  the  well- 
known  method  of  treating  with  zinc  dust  and  acetic  acid.  The  hydro- 

16° 
carbon  boils  at  90.5°-91°,  d  ^0.7497,  [<x]D  +  1.78°. 

l-Methyl-3-Ethylcyclopentane  was  prepared  in  an  optically  active 
form  by  Zelinsky  in  a  manner  similar  to  that  employed  for  the  1.3- 

16° 

dimethyl  derivative.     The  hydrocarbon  boils  at  120.5°-121°,  d  —^ 

0.7669,  [a]j)  +  4.34°.  It  is  noteworthy  that  the  optical  rotations  of 
the  active  saturated  hydrocarbons  are  usually  much  lower  than  the 
unsaturated  hydrocarbons  of  the  same  carbon  atom  structure. 

1-Methy  1-8-1  sopropy Icy clopentane'107  is  formed  by  reducing  cam- 
phorone by  Sabatier's  method  at  130°  to  dihydrocamphorone,  which 
on  further  reduction  yields  the  saturated  hydrocarbon,  boiling-point 
132°-134°,  d19°  0.773. 

1 .2-Dimethy 1-3-1 sopropy icy clopentane  10T  has  also  been  made  from 
camphorone  by  hydrogenation  to  dihydrocamphorone  and  treating  this 
ketone  with  methyl-magnesium  iodide,  decomposing  the  resulting  ter- 
tiary alcohol  and  hydrogenating  the  resulting  cyclopentene  derivative. 
The  saturated  hydrocarbon  boils  at  146°-148°,  d16°  0.786. 

1-Methy  1-2-1  sopropy  Icy  clopentane:  When  the  bicyclohexane  deri- 
vative prepared  by  Kishner  from  camphorone  by  his  hydrazine  method, 
is  treated  with  hydrogen  bromide  the  three-carbon  ring  is  broken  in 
such  a  way  as  to  form  a  cyclopentane  derivative,  a  very  general  result 
when  it  is  theoretically  possible  to  form  either  a  cyclopentane  or  cyclo- 
hexane  derivative  by  the  rupture  of  a  three-carbon  ring. 

H, H 


Decomposition  of  the  resulting  bromide  with  alcoholic  caustic  potash 
yields  the  isoprppylidene  derivative  almost  exclusively  but  decompo- 
sition by  aniline  gives  the  two  possible  isomers. 

Ber.  35,  2677   (1902). 

!4)  13,  599 


CYCLIC  NON-BENZEN01D  HYDROCARBONS 


273 


CH3 
CH, 


Both  of  the  above  unsaturated  hydrocarbons  on  catalytic  hydrogena- 
tion    yield    l-methyl-2-isopropylcyclopentane,    boiling-point    142.5°, 

d  ^  0.7833. 
U 

CYCLOPENTENES.    PHYSICAL  PROPERTIES  * 
Name  Formula  B.-P  °C 


Cyclopentene 

Methyl-A'-cyclopentene 

Methyl-A3-cyclopentene 

Ethyl  cyclopentene 

1  .l-dimethyl-A2-cyclopentene 

1  ^-dimethyl-A^cyclopentene 


CH, 


CH^- 
CH^ 


49  4 

44.5°        0.773  1.421 

69.  °        0.765  1.413 

72.  °        0.772  1.427 

— C2Hfl         108.  °        0.796  1.443 

78.  °        0.758  1.419 


CH, 


— CH,          103.  °        0.794        1.442 


CH, 


1.1.2-trimethyl-A«-cyclopen-     pfj  >1~~     ~\ 

tene  | / 

CHs 


108.  °        0.782        1.431* 


1  ^.S-trimethyl-A^yclopen- 
tene 


*Auwers,  Ann.  415,  110   (1918). 


>—  CH,          119.  °        0.796        1.442* 


20° 


**  The  refractive  indices  marked  with  an  asterisk  are  for  n — 

a. 


274      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

C2H6- 
1  l-diethyl-A2-cyclopentene     C2H5 ' 


144.  °        0.808        1.446 


C.H, 


1  ^-diethyl-A'-cyclopentene 


151.5°        0.812        1.452 


cyclopentene 


CH8 

140.  °        0.803        1.447* 


l'2tfnteriethyl"Al"CyCl°Pen'  '  ^-C2H5         181.5°        0.814        1.451* 


Naphthenic  Acids:  These  acids  probably  occur  in  more  petroleums 
than  is  commonly  supposed,  although  they  are  usually  associated  with 
Russian  petroleum.  The  naphthenic  acids  occurring  in  Russian  petro- 
leum include  relatively  simple  low-boiling  acids  so  that  the  mixture 
of  acids,  as  they  are  obtained  by  treating  with  aqueous  alkali  and 
precipitating  with  acid,  possesses  a  marked,  very  persistent  and  rather 
disagreeable  odor.  The  Gulf  Coast  petroleums  also  contain  organic 
acids  but  they  are  of  high  boiling-point  and,  when  separated  from  lu- 
bricating oil,  are  practically  odorless  and  are  easily  salted  out  of  their 
solutions  in  aqueous  solutions.  The  acids  in  the  Gulf  Coast  oils  have 
never  been  studied  to  the  extent  of  determining  their  nature,  but  their 
alkali  solutions  have  pronounced  emulsifying  and  foam  producing 
power  and  may  accordingly  find  employment  in  compounding  cutting 
oils  or  emulsions  but  can  hardly  be  employed  in  soaps  on  account  of 
the  ease  with  which  their  alkali  salts,  or  soaps,  are  salted  out. 

Markownikow  108  fractioned  the  methyl  esters  of  the  Russian  naph- 
thenic acids.  The  fraction  distilling  at  160°-165°  was  essentially 
CTHjACHg.  The  purified  free  acid  distilled  at  213°-214°  and  the 

20° 
purified  methyl  ester  boiled  at  164°-166°,  d  -^-  0.90509.    The  amide 

™Ann.  Sff!t  369   (1899). 


CYCLIC  NON-BENZEN01D  HYDROCARBONS  275 

melts  at  121°-123.5°  and  by  converting  the  amide  to  the  amine,  a 
secondary  amine  was  formed  which  is  perhaps  identical  with  the  sec- 
ondary amine  resulting  from  the  reduction  of  secondary  nitromethyl- 
cyclopentane.  The  acid  methylcyclopentane-2-carboxylic  acid 

CH2  — CH.CH3 

CH2 

CH2  —  CH.C02H 

isolated  by  Perkin  and  Freer,109  boils  at  219°-219.5°  and  an  isomeric 
acid,  probably  the  1.3  acid,  prepared  by  Euler,110  boils  at  220°.  The 
aldehyde  derivatives  of  methylcyclopentane  have  been  observed  by 
Markownikow  and  the  two  synthetic  acids  has  not  been  satisfactorily 
explained. 

The  starting  point  in  the  researches  of  Perkin  and  Freer lxl  was  the 
condensation  of  sodio-malonic  ester  with  1.4-dibromopentane, 
CH2  — CH  — CH3  C02R 

/  \  / 

CH,  Br          +  2Na  +  CH2 

CH2Br  C02R 


C02R 

On  heating  the  free  dicarboxylic  acid  a  few  degrees  above  its  melting- 
point  it  decomposes  to  carbon  dioxide  and  l-methylcyclopentane-2-car- 
boxylic  acid,  boiling-point  219.5°-220.5°.  These  carboxylic  acid  deri- 
vatives of  cyclopentane  are  of  interest  since  the  simpler  naphthenic 
acids  of  Russian  petroleum  are  evidently  derivatives  of  cyclopentane. 
The  acid  named  above  has  a  most  disagreeable  odor,  somewhat  resem- 
bling valeric  acid.  It  is  not  acted  upon  by  bromine  at  ordinary  tem- 
peratures but  at  100°  rapid  substitution  occurs  with  evolution  of  hy- 
drogen bromide. 

Zelinsky112  has  applied  the  Grignard  reaction  to  the  preparation  of 
naphthenic  acids  but  the  yields  are  usually  very  poor.    From  1-methyl- 

109  J.  Chem.  Soc.  53,  199   (1888). 

110  Ber.  28,  2952. 

111  J.   Chem.  Soc.  53,  195    (1888). 

112  Ber.  35,  2687   (1902). 


276      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


3-bromo-cyclopentane  the  acid  l-methylcyclopentane-3-carboxylic  acid 
was  prepared  by  passing  carbon  dioxide  into  the  ethereal  solution  of 
the  magnesium  derivative.  The  acid  distills  at  115°-116°  (15  mm.), 

ooo 

d  3S-  1.006;  the  amide  melts  at  149°-150°.  This  acid  is  possibly  iden- 
tical with  the  methylcyclopentanecarboxylic  acid  described  by  Euler, 
referred  to  above. 

Rearrangements  of  the  iodohydrins  of  the  methylcyclohexenes  to 
aldehyde  derivatives  of  methylcyclopentane  have-  been  lobserved  by 
Tiffeneau.113  Thus  the  iodohydrin  of  A3-methylcyclohexene,  on  treat- 
ing with  silver  nitrate  is  converted  into  the  aldehyde,  which  on  oxi- 
dation yields  the  corresponding  acid,  previously  obtained  by  Zelinsky, 


9H3 


H   OH 


CHO 


cqn 


The  iodohydrin  of  cyclopentene  does  not  rearrange  but  gives  the  1  .  2- 
oxide.  In  the  case  of  the  phenylcyclohexane  derivative  114  or  substi- 
tuted phenyl  derivatives,  rearrangement  to  the  cyclopentane  ring  does 
not  take  place  but  the  phenyl  group  migrates  to  the  a-position  with 
the  formation  of  a  cyclohexenol,  which  is  converted  to  the  isomeric 
ketone. 

Cydopentane-1  .2-Dicarboxylic  Acid  has  been  prepared  from  1.3- 
dibromopropane  and  sodium-malonic  ester  and  also  by  the  action  of 
iodine  on  the  disodium  derivative  of  the  ester, 


CH 


/ 

\ 


CH2  —  C  .  Na  (C02R) 


CH2  — C.Na(C02R) 


/ 

\ 


CH2  —  C  (C02R) 


CH2  — C(C02R) 


and  decomposing  the  tetracarboxylic  acid  by  heating,  in  the  usual 
manner, 

118  Compt.  rend.  159,  771   (1914). 

114  Le  Brazidec,  Compt.  rend.  159,  774   (1914). 


CYCLIC  NON-BENZENOID  HYDROCARBONS 
C0H. 


277 


CH 


CH2  —  C< 
/  I     C02H 


CH 


\ 


C02H 
C02H 


/ 
\ 


CH2  —  CH  —  C02H 


CH  —  CH  —  C02H 


It  is  known  in  cis  and  trans  forms,  the  cis  form  readily  forming  an 
anhydride. 

l-Methylcyclopentane-2.3-Dicarboxylic  Acid,  melting-point  99°- 
104°,  has  also  been  prepared  by  one  of  Perkin's  methods,  i.  e.,  condens- 
ing 1  .  3-dibromobutane  with  the  disodium  derivative  of  the  ethyl  ester 
of  ethane  tetracarboxylic  acid,  followed  by  decomposition  of  the  tetra- 
carboxylic  acid  in  the  usual  manner.115 

The  cis  and  trans  modifications  of  cyclopentane  1  .  2  .  4-tricarboxy- 
lic  acid  are  known,  and  are  best  prepared  by  the  reaction  of  ethyl  a(3-di- 
bromo-propionate  on  the  disodium  derivative  of  ethyl  propane-ct  a  y  y~ 
tetracarboxylate.116 


C(Na)< 


CH2 


\ 


C(Na)< 


C02R 
C02R 
C02R 
C0R 


BrCH2 
rCH. 


B 


C(C02R)2  —  CH2 
-»  CH2<  | 

C02R  C(C02R)2—  CHCO^R 


CCLH 


ie 


—  CH, 


CH. 


/ 
\ 


CH  — CH.CO2H 
.2H. 


vyj.0. 

CO, 


The  trans  form,  melting-point  129°-130°,  yields  the  anhydride  of  the 
cis  form  when  heated  with  acetic  anhydride  and  the  anhydride  then 
may  be  hydrolyzed  to  the  pure  cis  form,  melting  at  146°-148°. 


""Fargher,  J.  Ohem.  Soc.  U7,  1355   (1920). 

"•Perkin  &  Goldsworthy,  J.  Chem.  Soc.  105,  2666   (1914). 


Chapter  VIII.     The  Cyclic  Non-ben- 
zenoid  Hydrocarbons. 

The  Cyclohexane  Series. 

The  conception  of  cyclohexane  and  its  derivatives  as  "hydroaro- 
matic"  compounds  has  served  a  useful  purpose  in  connection  with  the 
study  of  the  constitution  of  benzene.  Reduction  of  ortho,  meta  and 
para  derivatives  of  benzene  yield  the  corresponding  derivatives  of 
cyclohexane  which  would  not  be  expected  from  Ladenburg's  prism 
formula.  It  has  also  been  shown  that  tetrahydrobenzene  and  dihydro- 
benzene  do  not  have  the  bridged  structures  shown  below, 

H  H2 

C  C 

/   \  /  \ 

H2C  CH2  HC          CH 

Hr~\  OTT  TTr^  OTT 

Z\U  Orlo  J3.VX  L/Jl 

\/  .       v 


C 
H 


H 


and  Baeyer  has  shown  that  the  tetrahydroterephthalic  acids  do  not 
possess  bridged  ring  structures  but  contain  double  bonds,  the  addition 
products  indicating  that  the  two  isomeric  acids  have  double  bonds  in 
the  two  positions  shown  below, 


and 


278 


THE  CYCLOHEXANE  SERIES 


279 


It  should  be  borne  in  mind  that  derivatives  of  hydrocarbons  such 
as  cyclohexane  are  capable  of  exhibiting  stereoisomerism  when  two 
or  more  substituents  are  present.  Thus  if  the  six  carbon  atoms  are 
conceived  to  lie  in  one  plane,  as  in  the  plane  of  the  paper,  then  six  of 
the  hydrogen  atoms  in  cyclohexane  will  lie  above  the  plane  and  six 
below  the  plane.  Cyclohexanecarboxylic  acid  can  obviously  exist  in 
only  one  form  but  a  cyclohexane  dicarboxylic  acid  can  exist  in  two 
forms.  Thus  the  1.4-dicarboxylic  acid  derived  from  terephthalic  acid, 
studied  by  Baeyer,  can  exist  in  two  stereo  isomeric  forms, 


H 
HO^C 


02H 
'H 


Baeyer  likened  these  stereoisomers  to  fumaric  and  male'ic  acids,  con- 
sidering the  double  bond  and  the  ring  structure  as  preventing  free 
rotation  in  much  the  same  manner, 

H          C02H 


o 


H  C02H 

male'ic  acid 


H02C  H 

\  / 

C 

/\ 


H 


maleinoid 
cyclohexane-1 .4- dicarboxylic  acid 


H 


C 


\ 


C02H 


H 

fumaric  acid 


fumdroid 
cyclohexane-1 .4- dicarboxylic  acid 


280       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

Cyclohexane  and  its  alkyl  derivatives  probably  occur  in  more  petro- 
leums than  is  generally  known  but  this  hydrocarbon  and  its  mono- 
methyl  and  dimethyl  derivatives  were  long  ago  recognized  as  impor- 
tant constituents  of  the  light  naphtha  from  Russian  petroleum,  hence 
the  term  "naphthenes"  suggested  by  Markownikow.  Careful  examina- 
tion of  the  lighter  distillates  of  the  petroleums  from  southern  Cali- 
fornia, Mexico  and  the  southern  Texas  and  Louisiana  fields  will  un- 
doubtedly show  the  presence  of  cyclohexane  and  its  simpler  alkyl  de- 
rivatives. *  Quite  a  variety  of  methods  have  been  employed  for  the 
preparation  of  cyclohexane  and  its  derivatives  but  the  methods  of  cat- 
alytic hydrogenation  of  Sabatier  and  Senderens  Ipatiev  and  Skita  are 
so  far  superior  to  most  of  the  others  that  the  latter  are  generally  only 
of  historical  interest.  A  number  of  syntheses  of  cyclohexane  and  its 
derivative  will  be  briefly  mentioned,  as  follows: 

(1)  Treatment  of  1 . 6-dibromohexane  with  sodium.1 

(2)  Reaction  of  1 . 5-dibromopentane,  malonic  ester  and  sodium 
ethylate,  yielding  cyclohexane-1 . 1-dicarboxylic  acid,  which  in  turn 
yields  cyclohexanecarboxylic  acid  by  decomposition. 

(3)  Heating  the  calcium  salt  of  pentane-1 . 5-dicarboxylic  acid, 
forming  cyclohexanone.2 

(4)  Condensation  of  the  ethyl  ester  of  pentane-1. 5-dicarboxylic 
acid  to  form  the  ester  of  cyclohexanone-2-carboxylic  acid. 

(5)  Condensation  of  two  molecules  of  succinic  ester  3  to  the  2.5- 
dicarboxylic  acid  derivative  of  the  1.4-cyclohexane-dione;  this  readily 
loses  C02  to  give  the  1.4-diketone,  which  can  be  reduced  by  the  usual 
methods  to  1 . 4-cy clohexanediol  from  which  cyclohexane  may  be  pre- 
pared by  reducing  with  hydriodic  acid  or  the  iodide  converted  into 
A1-4-cyclohexadiene. 

(6)  Condensation  of  8-ketonic  acids  to  1 . 3-cy clohexanediones. 

(7)  Addition  of  sodium  malonic  ester  to  a  (3  unsaturated  ketones 
to  form  derivatives  of  1.3-cyclohexanedione. 

(8)  Condensation  of  two  molecules  of  acetoacetic  ester  with  alde- 
hydes to  form  open  chain  diketonic  acids  which  condense  further  to 
cyclic  unsaturated  ketonic  esters  which  readily  lose  C02  on  saponifi- 
cation  to  give  cyclohexenone  derivatives.     Similar  products  are  ob- 
tained by  the  condensation  of  methylene  iodide  and  two  molecules  of 
sodium  acetoacetic  ester.4 

aW.  H.  Perkin,  Jr.,  Ber.  27,  216   (1894). 

2  Markownikow,  Compt.  rend.  110,  466   (1890)  ;  115,  462   (1892). 
'Baeyer,  Ann.  Htf,  106   (1888)  ;  Ber.  23f  1276   (1890). 
«Hagemann,  Ber.  26,  876  (1893). 


THE  CYCLOHEXANE  SERIES  281 

(9)  Condensation  of  aliphatic  aldehydes  and  ketones,   for  ex- 
ample, methyl  heptenone  to  a  mixture  of  meta-xylene  and  dimethyl- 
cyclohexene;  citronellal  to  isopulegol,  etc. 

(10)  Addition  of  chlorine  to  benzenoid  hydrocarbons,  for  example, 
the  addition  of  chlorine  to  benzene  to  form  hexachlorocyclohexane. 

(11)  The  indirect  reduction  of  unsaturated  substances  by  first 
adding  bromine  or  hydrobromic  acid  and  then  replacing  the  bromine 
by  hydrogen  by  treating  with  acetic  acid  and  zinc,  for  example  the 
conversion  of  dihydro  and  tetrahydroterephthalic  acids  to  cyclohexane- 
1.4-dicarboxylic  acid. 

(12)  The  hydrogenation  or  reduction  of  benzenoid  hydrocarbons. 
As   mentioned   above,   these  methods,   particularly   the   well-known 
method  of  Sabatier  and  Senderens,  have  practically  superseded  all  the 
older  methods  and  promise  to  become  of  industrial  importance  for 
the  hydrogenation  of  benzene  to  cyclohexane,  phenol  to  cyclohexanol 
and  cyclohexanone,  both  the  latter  products  being  of  value  as  com- 
mercial solvents  (see  below).    The  ease  of  reduction  or  hydrogenation 
varies  considerably  with  the  number  and  character  of  the  substituent 
groups.  Thus  terephthalic  acid  and  the  dihydro  and  tetrahydro-tereph- 
thalic  acids  are  reduced  with  difficulty,  but  mellitic  acid  is  easily  re- 
duced by  reducing  agents  to  cyclohexanehexacarboxylic  acid. 


HOC 

3 

:o2H 

With  the  phenols  the  ease  of  reduction  increases  with  the  number  of 
hydroxyl  groups,  resorcin  being  easily  reduced  to  cyclohexane-1.3- 
dione. 

Benzene  is  reduced  to  cyclohexane  in  the  presence  of  catalytic 
nickel  at  180°-250°,  but  the  refinements  of  the  process  as  earned  out 
industrially  are  not  generally  known.  Cyclohexane  was  manufactured 
in  this  way  in  the  United  States  and  in  Germany  during  the  recent  war, 
the  cyclohexane  being  used  to  some  extent  as  a  motor  fuel 5  for  aero- 
planes. In  the  case  of  the  alkyl  derivatives  of  benzene  some  decompo- 

8  Dayton  Metal  Products  Co.  Brit.  Pat.  133,288;  133,667    (1919). 


2®      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

sition  also  takes  place,  for  example,  in  the  hydrogenation  of  para- 
cymene  at  170°-180°  to  para-menthane,  small  proportions  of  methyl 
and  ethylcyclohexane  are  also  formed.  At  about  300°  the  mixture  in 
equilibrium  in  the  presence  of  nickel  consists  chiefly  of  benzene  and 
at  this  temperature  dehydrogenation  of  cyclohexane  to  benzene  can  be 
effected.  The  relative  ease  with  which  this  change  is  brought  about 
makes  possible  the  detection  of  small  proportions  of  cyclohexane  in 
the  presence  of  normal  hexane,  and  other  saturated  hydrocarbons,  the 
fraction  distilling  at  75°-85°  being  passed  over  nickel  at  300°  and  the 
distillate  treated  with  concentrated  sulfuric  acid  to  remove  and  poly- 
merize defines  and  then  treated  with  nitrating  acid  mixture  to  remove 
the  benzene  which  may  be  identified  as  crystalline  dinitrobenzene.6 
As  regards  the  hydrogenation  of  benzene  to  cyclohexane  by  hydrogen 
in  the  presence  of  platinum  black  Willstatter  and  Hatt 7  show  that  the 
reaction  proceeds  quantitatively  at  atmospheric  pressures  in  about  six 
hours  in  glacial  acetic  acid  solution,  using  about  0 . 1  part  of  platinum 
black.  The  hydrogenation  is  distinctly  slower  when  glacial  acetic  acid 
is  not  used  as  a  solvent.  The  catalyst  is  exceedingly  sensitive  to  traces 
of  thiophene,  less  than  0.01  mg.  of  thiophene  per  gram  of  benzene  com- 
pletely preventing  the  hydrogenation.  Toluene  is  reduced  to  methyl- 
cyclohexane  under  the  same  conditions  much  more  readily  than  in  the 
case  of  benzene,  i.  e.,  in  about  3%  hours. 

The  hydrogenation  of  benzene  derivatives  to  the  corresponding  de- 
rivatives of  cyclohexane  may  conveniently  be  considered  here.  As- 
chan 8  reduced  sodium  benzoate  by  sodium  amalgam,  neutralizing  the 
caustic  soda  by  carbon  dioxide,  as  fast  as  formed,  thus  preventing 
the  precipitation  of  the  sodium  benzoate  by  the  concentrated  caustic 
soda.  When  the  hydrogenation  is  incomplete  a  considerable  pro- 
portion of  A2-cyclohexene  carboxylic  acid  is  formed.  Ipatiev 9  ob- 
tained yields  of  40  to  50  per  cent  of  cyclohexane  carboxylic  acid  by 
his  method  of  reducing  at  300°-320°  and  hydrogen  at  about  210  atmos- 
pheres in  the  presence  of  nickel  oxide.  Phthalic  acid  under  the  same 
conditions  is  more  readily  reduced  to  the  corresponding  cyclohexane- 
1.2-dicarboxylic  acid  and  this  method  is  probably  the  best  method  of 

•Tausz,  Chem.  Ztg.  37,  334  (1914).  According  to  Zelinsky  (Cf.  Wieland,  Ber.  tf, 
484  [1912]),  hydrogen  is  dissociated  from  cyclohexane,  with  the  formation  of  benzene, 
at  temperatures  below  300°  and  in  the  presence  of  nickel ;  under  the  same  conditions 
cyclopentane  and  cycloheptane  are  stated  to  be  practically  unchanged.  In  the  absence 
of  a  catalyst  cyclohexane  yields  considerable  benzene  at  490° ;  normal  hexane  at 
sightly  higher  temperatures  yields  methane,  amylene  and  other  hydrocarbons.  (Jones, 
.7.  Chem.  Hoc.  107.  1582  [1915].) 

7  Ber.  tff  1471  (1912). 

8  Ber.  24,  1864    (1891). 
•Ber.  41,  1005    (1908). 


THE  CYCLOHEXANE  SERIES  283 

preparing  this  acid.  It  is  noteworthy  that  at  the  same  temperatures 
and  with  the  same  catalyst  but  without  the  use  of  pressure  no  hydro- 
genation  of  phthalic  acid  could  be  detected.  The  older  method  of  re- 
duction by  means  of  sodium  and  amyl  alcohol  was  used  successfully 
for  the  reduction  of  anthranilic  acid  to  2-amidocyclohexanecarboxylic 
acid,  and  also  para-amidobenzoic  acid  to  4-amidocyclohexanecarboxy- 
lic  acid.10  Osterberg  and  Kendall 1X  used  sodium  and  alcohol  for  the 
reduction  of  the  oxime  of  cyclohexanone  to  cyclohexylamine  and  also 
report  that  the  method  of  Sabatier  and  Senderens  gives  good  yields  of 
the  amine  from  the  oxime,  but  state  that  the  method  of  reducing  aniline 
to  cyclohexylamine,  according  to  Ipatiev,  did  not  give  satisfactory  re- 
sults. Ipatiev  reported  yields  of  40  to  50  per  cent  of  the  amine  by 
reducing  aniline  with  hydrogen  and  nickel  oxide,  employing  a  hydro- 
gen pressure  of  about  120  atmospheres  at  220°-230°.  Quinoline  could 
not  be  hydrogenated  by  Padoa  and  Carughi,12  using  the  method  of  Sa- 
batier and  Senderens,  but  Ipatiev  succeeded  in  reducing  it  to  deca- 
hydroquinoline  by  his  high  pressure  method.  Diphenylamine  also  can- 
not be  reduced  to  dicyclohexylamine  by  the  Sabatier  and  Senderens 
method,  other  products  being  formed,  but  the  Ipatiev  method,  at  225°- 
230°,  gives  a  good  yield  of  dicyclohexylamine.13  Paals'  method  on 
aniline  is  reported  to  give  a  yield  of  about  10  per  cent  of  cyclohexyl- 
amine. Osterberg  and  Kendall  recommend  Ipatiev 's  method  for  the 
preparation  of  cyclohexane  and  cyclohexanol.  Ipatiev  finds  that  nickel 
oxide  hydrogenates  benzene  and  its  derivatives  several  times  faster 
than  reduced  nickel  in  the  presence  of  hydrogen  under  pressure  at 
about  255°.  The  cyclohexane  so  produced  is  practically  pure  and  the 
reduction  is  complete  in  about  iy2  hours  when  using  2  g.  nickel  oxide 
to  25  g.  benzene.  Decomposition  with  the  formation  of  methane  and 
the  separation  of  carbon  begins  to  be  noticeable  at  about  290°.  Un- 
der the  same  conditions  Ipatiev  reduced  phenol  to  cyclohexanol,  di- 
phenyl  to  dicyclohexyl,  naphthalene  (in  two  successive  operations)  to 
decahydronaphthalene,  dibenzyl  to  dicyclohexylethane,  (3-naphthol  to 
p-hydroxydecahydronaphthalene  and  a-naphthol  to  a-hydroxydecahy- 
dronaphthalene.  Anthracene  was  reduced  by  Godchot 14  by  reduced 

10Einhorn  &  Meyenburg,  Ber.  27,  2466  (1894).  In  the  case  of  anthranilic  acid  the 
reaction  proceeds  in  two  ways,  pimelic  acid  also  being  formed,  probably  through  the 
intermediate  formation  of  salicylic  acid. 

NH2  OH  CH2CH2CO2H 

C8H4<  >  CaH4<  +  H.,0  +  4H »     | 

C02H  C02H  CH2CH2CH2C02H 

11  J.  Am.  Chem.  Soc.  42,  2616  (1920). 

™Atti.  Accad.  Lincei   (5)   15,  113   (1907). 

"Ipatiev,  Ber.  41,  991   (1908)  ;  40,  1281   (1907). 

"Compt.  rend.  139,  605   (1904). 


284      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

nickel  at  atmospheric  pressure  to  tetra  and  octohydroanthracene,  but 
Ipatiev  succeeded  in  completely  reducing  it  to  perhydroanthracene, 
C14H24,  by  his  high  pressure  method,  using  nickel  oxide  as  a  catalyst. 
By  one  operation  tetrahydroanthracene,  melting-point  103°-105°,  is 
the  chief  product;  a  second  operation  yields  mainly  decahydroanthra- 
cene,  C14H20,  melting-point  73°-74°,  and  a  third  operation  using  the 
decahydroanthracene  yields  the  completely  reduced  hydrocarbon, 
C14H24,  melting-point  88°-89°.  Slight  carbonization  and  formation 
of  methane  occurs  at  the  temperatures  employed,  i.  e.,  260°-270°. 
Phenanthrene  was  also  reduced  in  steps,  the  completely  reduced  hydro- 
carbon being  finally  obtained.  At  lower  temperatures  the  hydrocar- 
bon was  not  completely  reduced,  the  temperatures  required  being  con- 
siderably higher  than  for  the  reduction  of  benzene, 

At  320°  phenanthrene  >    chiefly  C14H12  and  C14H14 

At  360°  "  — >         "      C14H18 

At  370°  "  — >         "      C14H24 

The  completely  reduced  phenanthrene  is  a  liquid  boiling  at  270°-276°, 
does  not  crystallize  at  — 15°  and  is  inert  in  the  cold  to  nitrating  acid 
mixture,  bromine  and  aqueous  permanganate.  Phenyl  ether  is  decom- 
posed under  the  conditions  of  Ipatiey's  method,  yielding  a  mixture  con- 
sisting of  cyclohexane,  cyclohexanol  and  cyclohexyl  ether  (temperature 
employed  230°). 

As  regards  the  practicability  of  developing  Ipatiev's  method  into 
an  industrial  process,  it  may  be  pointed  out  that  the  pressures  employed 
are  at  least  no  higher  than  the  lowest  pressures  employed  for  the  syn- 
thesis of  ammonia  from  nitrogen  and  hydrogen,  and  the  temperatures 
required  are  very  much  lower.  The  technique  of  operating  at  such 
pressures  on  an  industrial  scale  has  been  improved  to  a  degree  which 
should  make  Ipatiev's  process  entirely  feasible  industrially.  In  con- 
nection with  the  hydrogenation  of  complex  benzenoid  hydrocarbons  it 
should  be  noted  that  attempts  have  recently  been  made  to  hydrogenate 
coal  under  high  pressures  to  oily  hydrocarbon  mixtures  from  which 
oily  hydrocarbons,  or  polynaphthenes  having  lubricating  value,  may 
be  obtained.  This  work,  the  details  of  which  are  not  yet  available,  are 
undoubtedly  based  upon  the  earlier  findings  of  Bergius  15  that,  under 

15  According  to  U.  S.  Pat.  1,342,790,  issued  to  F.  Bergius,  pulverized  coal  is  mixed 
with  a  mineral  oil  boiling  above  200°  and  introduced  as  a  thick  paste  into  a  reaction 
vessel,  where  it  is  heated  to  about  400°  and  subjected  to  the  action  of  hydrogen,  with- 
out introducing  any  catalytic  substance,  under  a  pressure  of  100  atmospheres.  Partial 
hydrogenation  is  claimed,  a  heavy  oil  boiling  about  300°-400°  being  formed  from  the 
coal  substance.  Bergius  claims  that  with  soft  coals  as  much  85%  of  the  coal  may 
thus  be  converted  into  oily  liquid  or  oil  soluble  products. 


THE  CYCLOHEXANE  SERIES  285 

very  high  pressures,  hydrogenation  can  be  effected  without  &  catalyst. 
For  the  hydrogenation  of  such  an  impure  material  as  coal,  it  is  obvious 
that  either  a  high  pressure  method  of  the  Bergius  type,  or  the  em- 
ployment of  a  catalyst  not  poised  by  sulfur,  will  be  required. 

Skita  has  shown  that  the  benzene  ring  may  be  reduced  at  ordinary 
temperatures  by  colloidal  platinum.  Thus  cinnamic  aldehyde  is  con- 
verted into  cyclohexyl  propyl  alcohol  by  reduction  in  this  way  using 
very  slight  pressures,  i.  e.,  about  one  atmosphere.  Cyclohexanone  is 
also  very  rapidly  reduced  to  cyclohexanol  in  the  same  manner.  Acetic 
acid  is  usually  employed  as  a  solvent.  The  unsaturated  ketone  pu- 
legone  also  yields  the  saturated  alcohol  menthol  under  the  same  con- 
ditions.16 For  research  and  laboratory  preparations,  Skita's  method 
is  usually  to  be  preferred  although  the  method  does  not  appear  to  have 
been  applied  to  many  reductions  of  the  benzene  nucleus.  Aqueous 
alcohol  may  also  be  employed  as  a  solvent.  In  the  reduction  of 
pulegone  to  menthol  5  grams,  in  40  c.c.  acetic  acid,  and  with  colloidal 
platinum  and  a  little  gum  arabic  as  a  protective  colloid  to  retard  pre- 
cipitation of  the  metal,  the  reduction  is  complete  in  sixty  minutes. 

Cyclohexane:  The  presence  of  cyclohexane  in  Russian  petroleum 
was  shown  by  Markownikow 17  and  Young  found  it  also  in  a  specimen 
of  gasoline  from  an  American  petroleum,  but  the  exact  origin  of  the  oil 
examined  by  Young  is  not  known.  Its  presence  in  the  fraction  boiling 
at  80°-81°  may  be  indicated  by  the  physical  constants  of  the  fraction 
and  the  isolation  of  adipic  acid  among  the  products  of  oxidation  by 
nitric  acid.  The  boiling-point  is  usually  given  as  80.8°,  but  the  physi- 
cal properties  of  a  specimen  of  the  hydrocarbon  carefully  purified  by 
several  treatments  with  slightly  fuming  sulfuric  acid  are  given  by 

11  2° 
Auwers18  as  follows,  boiling-point  80.0°-80.2°  at  749  mm.,  d   -^- 

0.7869,  nD  1.42910,  MD  27.66  (calculated  27.71). 

Cyclohexane  is  slightly  more  stable  to  heat  than  normal  hexane,  but 
the  decomposition  of  both  is  noticeable  at  500°  and  under  pressure. 
According  to  Ipatiev 19  it  is  decomposed  at  500°-510°  and  in  the  pres- 
ence of  alumina  (110  atmospheres  pressure)  to  a  complex  mixture  of 
decomposition  products  among  which  methyl  cyclopentane  was  identi- 
fied by  means  of  the  easily  formed  tertiary  nitro  derivative 

16  Ber.  tf,  1496  (1915). 

11  Ber.  SO,  974  (1897). 

18  Ann.  410,  262  (1915). 

»  J.  Ruse.  Phys.-Chem.  Soc.  tf,  1431  (1912). 


286       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

CH2-CH2  N02 

A>C<  Cyclohexane  is  practically  inert  to  bro- 

H2  — CH2  CH3 

mine  in  the  cold  and  is  only  very  slowly  reacted  upon  at  its  boiling- 
point  and  in  diffused  daylight,  but  bromination  is  rapid  in  direct  sun- 
light. In  the  presence  of  anhydrous  aluminum  bromide  a  mixture  of 
high  boiling  products  is  formed,  but  when  dibromo  cyclohexane  or 
cyclohexene  is  similarly  treated  it  is  possible  to  identify  hexabromo- 
benzene  among  the  reaction  products.20 

Considerable  has  been  written  about  the  so-called  "jormolite"  re- 
action which,  according  to  Nastjukow,  the  cyclohexenes  and  other  non- 
benzenoid  cyclic  hydrocarbons  undergo  when  treated  with  formalde- 
hyde in  the  presence  of  concentrated  sulfuric  acid  or  aluminum  chlo- 
ride. According  to  Nastjukow  21  a  mixture  of  cyclohexane,  anhydrous 
aluminum  chlorine  and  trioxymethylenes  react  forming  a  mixture  of 
condensation  products  but  no  definite  reaction  product  was  isolated. 
The  reaction  is  usually  carried  out  using  sulfuric  acid  as  the  condens- 
ing reagent  and  the  saturated  acyclic  hydrocarbons  are  supposed  not 
to  give  the  "formolite"  reaction.  It  does  not  appear  that  any  definite 
reaction  products  have  ever  been  isolated  and  the  character  of  the 
reaction  therefore  is  at  present  a  matter  of  speculation;  also  it  does 
not  appear  that  the  reaction  has  been  carried  out  with  a  sufficient  num- 
ber of  pure  hydrocarbons  to  warrant  the  proposal  that  it  be  employed 
in  the  study  of  petroleum  fractions  to  determine  what  types  of  hydro- 
carbons are  present.  As  carried  out  according  to  Nastjukow  one  vol- 
ume of  the  hydrocarbon  mixture  is  treated  with  one  volume  of  concen- 
trated sulfuric  acid  and  then  one-half  volume  of  concentrated  (40%) 
formaldehyde  is  gradually  added,  with  agitation.  A  precipitate  is 
formed  which  after  washing  with  gasoline,  water  and  ammonia,  may 
be  dried  and  powdered,  the  product  resembling  a  brown  re'sin.  The 
higher  boiling  oils  generally  yield  larger  proportions  of  "formolite" 
resin  than  the  lighter  oils,  but  the  yield  of  resin  appears  to  vary  evi- 
dently with  the  conditions  of  the  operation.  The  product  prepared 
according  to  Nastjukow's  directions  contains  considerable  sulfur,  a 
spindle  oil  giving  a  resin  containing  6.98  per  cent  sulfur  and  6.66  per 
cent  oxygen.  When  the  mixture  is  kept  cold  the  condensation  product 
is  liquid  and  does  not  contain  sulfur.22  According  to  Gurwitsch  23  only 

20  Bodroux  &  Taboury,  Bull.  soc.  chim.  9,  592   (1911). 
21 J.  Russ.  Phys.-Chem.  Soc.  J7,  46   (1915). 
™J.  Russ.  Phus.-CJiem.  Soc.  W,  1596    (1910). 
28  Wissensch,  Grundlagen  d.  Erdolbearb.,  46. 


THE  CYCLOHEXANE  SERIES  287 

certain  defines  such  as  "partially  reduced  aromatic  compounds"  and 
aromatic  hydrocarbons  react  to  give  formolite  resins.  Terpenes  are 
said  to  give  "formolite"  resins,  but  they  are  very  energetically  poly- 
merized, oxidized  and  esterified  by  sulfuric  acid  alone  and  it  is  en- 
tirely obscure  what  the  function  of  the  formaldehyde  is  supposed  to 
be.  Most  books  on  petroleum  testing  describe  the  "formolite"  reaction 
and  often  use  the  phrase  "formolite  number,"  but  this  test  and  these 
phrases  are  meaningless  until  the  reaction  is  studied  in  many  cases,  not 
only  of  cyclohexane,  the  cyclohexenes,  and  commercial  oils  of  known 
chemical  character,  but  also  applied  to  a  series  of  definite  pure  hydro- 
carbons of  various  types.  Cyclohexenes  should  give  "formolite"  resins 
since  they  polymerize  readily  with  sulfuric  acid  alone  and  cyclohexa- 
diene  reacts  violently  with  sulfuric  acid.  Nastjukow  may  have  dis- 
covered something,  but,  if  so,  no  one  has  been  able  to  determine  what 
it  is. 

A  series  of  metallo  derivatives  of  cyclohexane  has  been  prepared  by 
Griittner,24  who  has  prepared  cyclohexyl  derivatives  of  lead,  tin  and 
bismuth.  The  starting  point  in  all  cases  was  the  reaction  of  cyclohexyl 
magnesium  bromide  on  the  chloride  or  bromide  of  the  other  metal. 
Bromocyclohexane  reacts  with  magnesium  in  ether  very  much  like 
n .  hexyl  bromide,  the  secondary  reaction 

RMgBr  +  R.Br-     — »  MgBr2  +  R.R., 

taking  place  in  both  cases.     The  cyclohexyl  derivatives  show  slight 
differences  from  the  simple  alkyl  derivatives  of  lead.    Tetracyclohexyl 
lead  reacts   with  hydrogen   chloride   or  hydrogen   bromide  to   give 
X2 

Pb  and  the  simple  alkyl  derivatives  give  Pb  X .  R3  under 

(CAi), 

the  same  conditions.  Cyclohexyl-magnesium  bromide  and  lead  chlo- 
ride in  ether  react  very  smoothly.  Tetracyclohexyl  tin  crystallizes  in 
fine  microscopic  aggregate  melting  at  248°  and  is  easily  soluble  in  ben- 
zene, chloroform  and  carbon  bisulfide;  bromine  reacts  with  it  to  give 
SnBr2  (CgHnJz,  long  well  formed  needles  melting  at  58°.  Tiffeneau 
and  Gannage  25  prepared  dicyclohexyl-mercury  by  the  action  of  sodium 
amalgam  on  bromocy clohexane ;  the  mercury  derivative  forms  needles 
of  a  camphor-like  odor,  melting  at  139°.  Mercury  derivatives  of 

"Ber.  47,  3257   (1914). 

"  J.  Chem.  Soc.  At s.  120  (1),  472  (1921). 


288      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

methylcyclohexane  were  similarly  prepared  from  4-bromomethylcyclo- 
hexane.  Derivatives  of  the  type  RHgCl  were  made  from  dicyclohexyl- 
mercury  by  the  action  of  benzoyl  chloride  or  arsenic  trichloride. 

Some  Simple  Derivatives  of  Cyclohexane:  An  extensive  review  of 
the  derivatives  of  cyclohexane  is  beyond  the  scope  and  purpose  of  the 
present  volume  but  a  brief  description  of  some  of  the  more  important 
derivatives  indicating  the  close  parallelism  in  the  chemistry  of  cyclo- 
hexane and  normal  hexane,  and  other  examples  of  chemical  behavior 
which  are  likely  to  prove  of  interest  in  connection  with  the  chemical 
investigation  of  petroleum,  are  given. 

Cyclohexane  is  readily  acted  upon  by  dry  chlorine,  direct  sunlight 
not  being  required.  The  monochloride,  boiling-point  141.6°-142.6°, 

22° 
d  -pr^-  0.9976,  is  also  readily  prepared  by  the  action  of  concentrated 

hydrochloric  acid  or  PC13  on  cyclohexanol.  On  treating  with  alkalies 
the  chloride  forms  cyclohexene  and  when  alcoholic  caustic  alkalies  are 
employed  a  small  proportion  of  cyclohexylethyl  ether  is  formed;  in  fact, 
the  behavior  of  the  chloride  closely  parallels  the  behavior  of  the  mono- 
chloron.  hexanes.  Like  the  monochloropentanes  and  monochloro- 
hexanes  the  cyclohexyl  derivative  is  decomposed  by  passing  over  anhy- 
drous barium  chloride  or  alumina  at  350°-450°,  cyclohexene  being 
formed  almost  quantitatively.26  Another  process  for  converting  chloro- 
cyclohexane  to  cyclohexene  describes  passing  the  chloride  over  lime  at 
350°-450°  or  over  barium  chloride  at  300°-400°.27  Fortey  28  decom- 
posed the  chloride  by  heating  with  quinoline  and  described  the  result- 

4° 
ing  cyclohexene  as  boiling  at  82.3°  d  — 0.8244,  but  Auwers  29  gives  the 

15  6° 

following  physical  constants,  boiling-point  83°-83.5°  (760  mm.),  d     ' 

0.8143,  nD  1.44921,  MD  27.03  (calculated  MD  27.24).  Cyclohexene 
cannot  be  made  satisfactorily  from  cyclohexanol  by  heating  with  an- 
hydrous oxalic  acid,  the  principal  product  being  dicyclohexyl  oxalate, 
but  heating  with  potassium  acid  sulfate  gives  an  80  per  cent  yield  of 
cyclohexene.30  A  small  proportion  of  cyclohexyl  ether,  boiling-point 
239°-240°,  is  also  formed.  The  bromine  and  iodine  derivatives  are 
naturally  more  easily  decomposed  than  the  chlorides,  but  a  double  bond 
adjacent  to  the  halogen  stabilizes  the  substance  as  in  the  aliphatic  se- 

2a  Badische,  Anilin  n.  Soda  Fabr.,  J.  C'hem.  Soc.  Abs.  1913  (1),  349. 

27  Schmidt,  Hochschwender  &  Eichler,  Chem.  Abs.  1917,  1885. 

28  J.  Chem.  Soc.  73,  941   (1898). 

29  Ann.  JklO.  257   (1915). 

80  Willstatter  &  Hatt,  Ber.  tf,  1464  (1912). 


THE  CYCLOHEXANE  SERIES 


289 


ries.  Usually  the  halogen  derivatives  have  not  been  prepared  from  the 
hydrocarbon  but  from  the  alcohols.  Thus  cyclohexanol  and  concen- 
trated hydriodic  acid  yield  cyclohexyl  iodide  and  quinite  yields  the 
corresponding  1.4  dihalogen  derivatives. 

When  cyclohexane  is  chlorinated  in  the  cold  a  mixture  of  chlorides 
is  obtained.  Two  dichlorocyclohexanes  are  obtained,  one  boiling  at 
105.4°-106.4°  (50  mm.)  and  the  other  distilling  at  112.4°-113.4° 
(50  mm.)  ;  the  former  on  prolonged  boiling  with  alcoholic  caustic  pot- 
ash yields  a  chlorocyclohexene.  On  distilling  at  atmospheric  pressure 
the  dichlorides  decompose  markedly.  Continued  chlorination  yields 
tetrachlorocyclohexane,  crystallizing  from  chloroform  in  long  prisms 
melting  at  1730.81 

Cyclohexane  is  practically  unacted  upon  by  the  usual  nitrating 
mixture  of  nitric  and  sulfuric  acids,  but  may  be  nitrated  by  heating  in 
a  sealed  tube  with  dilute  nitric  acid  according  to  the  method  discovered 
by  Konowalow.32  Its  behavior  in  this  respect  is  practically  identical 
with  that  of  n.hexane  and  the  properties  of  the  resulting  nitrocyclo- 
hexane  are  quite  different  from  the  properties  of  nitrobenzene.  On 
reduction  with  tin  and  hydrochloric  acid,  the  corresponding  amine  is 
not  formed  but  cyclohexanone  or  its  condensation  products  are  formed, 
evidently  through  the  intermediate  formation  of  the  oxime  of  cyclo- 
hexanone, 


\NQ, 


i50  form 


oxime 


clohexanone 


Dinitro  and  trinitro  derivatives  of  cyclohexane  cannot  be  prepared  by 
the  nitration  method  noted  above.  Alkyl  derivatives  of  cyclohexane, 
such  as  methyl  or  dimethylcyclohexane,  containing  a  tertiary  hydro- 
gen atom  are  much  more  easily  nitrated  by  Konowalow's  method,  the 
nitro  group  replacing  the  tertiary  hydrogen  atom.  Like  primary  and 
secondary  nitro  derivatives  of  the  aliphatic  series,  nitrocyclohexane  is 
soluble  in  alkalies,  evidently  forming  salts  of  the  iso  form  whose  struc- 
ture is  noted  above.  Nitro  cyclohexane  boils  at  205.5°,  d20°  1.0616. 


"Sabatier  &  Mailhe,  Compt.  rend.  137,  240  (1903). 
"Compt.  rend.  121,  652   (1895). 


290      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

Nametkin 83  states  that  the  yield  of  nitrocyclohexane  is  increased  by 
nitrating  the  hydrocarbon  with  about  three  parts  by  weight  of  alu- 
minum nitrate.  Cyclohexane  yields  about  56  per  cent  of  nitro- 
cyclohexane together  with  cyclohexanone  and  dinitrodicyclohexyl, 
C12H20(N02)2  melting  at  216.5°. 

Aminocyclohexane  and  other  amino  derivatives  of  the  cyclohexanes 
differ  markedly  from  the  amines  of  the  benzene  hydrocarbons,  par- 
ticularly in  their  behavior  when  treated  with  nitrous  acid.  As  noted 
above  aminocyclohexane  is  best  prepared  by  reduction  of  the  oxime 
of  cyclohexanone  in  alkaline  solution  or  by  catalytic  hydrogenation  by 
the  Sabatier  and  Senderens  method.  Heating  cyclohexanone  or  similar 
ketones  with  ammonium  formate  and  reduction  of  the  resulting  formyl 
derivative  to  the  amine  has  also  occasionally  been  employed,34  but  re- 
duction of  the  oxime  generally  gives  much  better  yields.  In  the  case 
of  tertiary  nitro  compounds,  such  as  1 -nitro- 1-methy  Icy  clohexane,  re- 
duction of  the  nitro  group  gives  satisfactory  yields  since  the  tertiary 
nitro  derivatives  cannot  rearrange  to  the  iso  forms  with  the  resulting 
formation  of  oximes  and  ketones. 

The  aminocyclohexanes  yield  comparatively  stable  nitrites  when 
treated  with  nitrous  acid  and  on  heating  their  aqueous  solutions  de- 
composition takes  place  with  difficulty  yielding  the  corresponding  alco- 
hol (yields  usually  very  poor),  and  decomposition  also  proceeds  in 
another  manner  with  the  formation  of  ammonia  and  unsaturated  hy- 
drocarbons. The  latter  reaction  can  be  modified  so  as  to  serve  admir- 
ably for  the  preparation  of  unsaturated  hydrocarbons,  particularly  in 
cases  where  the  resulting  unsaturated  hydrocarbon  is  easily  rearranged 
or  polymerized.  For  this  purpose  the  amine  is  subjected  to  exhaustive 
methylation  and  the  resulting  alkylated  ammonium  hydroxide  decom- 
posed by  gentle  heating,  a  method  mentioned  in  connection  with  cyclo- 
butene  and  which  warrants  more  extensive  applications  in  research. 
Decomposition  of  the  phosphates  of  amines  of  this  type  by  heating  has 
also  been  employed  for  converting  the  amines  to  unsaturated  hydro- 
carbons.85 

The  method  of  reducing  the  oximes  to  amines  has  been  employed 
for  the  preparation  of  the  1.3-diamine  and  1.4-diamine,  the  oximes 
being  prepared  from  the  corresponding  ketones.  The  1 . 2-diamine  has 
been  prepared  from  anthranilic  acid  which  can  be  best  reduced  by  the 

UJ.  Russ.  Phvs.-Chem.  Soc.  42,  581   (1910). 
"Leuchart  &  Bach,  Ber.  20,  104   (1887). 
"Harries,  Ber.  S^  300  (1901). 


THE  CYCLOHEXANE  SERIES 


291 


method  of  Ipatiev  or  by  sodium  and  amyl  alcohol.36  The  amide  of  the 
reduced  acid  may  then  be  converted  to  the  diamine  in  the  usual  manner 
by  bromine  and  alkali.37 

The  cyclohexadienes  have  been  of  considerable  interest  on  account 
of  their  close  relation  to  benzene.  A  cyclohexadiene  boiling  at  84°-86° 
was  first  made  by  Baeyer 38  and  the  same  laborious  methods  of  prepa- 
ration were  later  employed  by  Crossley.39  A  product  evidently  identi- 
cal with  Baeyer's  and  having  the  same  boiling-point  was  made  by 
Markownikow  by  decomposing  chlorinated  cyclohexane  isolated  from 
Russian  petroleum.40  Fortey  reported  a  cyclohexadiene  boiling  at  81°- 
82° 41  and  Harries  and  Antoni 42  obtained  a  product  of  the  same  boiling- 
point,  81.5°,  by  the  decomposition  of  the  phosphate  of  1.4-diamino- 
cyclohexane.  From  1 . 2-dibromocyclohexane  Crossley43  also  obtained 
the  low-boiling  product  and,  from  its  method  of  preparation  and  the 
fact  that  oxidation  by  nitric  acid  yielded  oxalic  and  succinic  acids,  con- 
cluded that  the  low-boiling  product  was  1 . 3-cyclohexadiene. 


CH, 


CIL 


CO,H. 


C02H      C02H       C02H. 


Zelinsky  and  Gorsky  44  obtained  the  high-boiling  hydrocarbon  from 
1.4  dibromocyclohexane  and  the  low-boiling  one  from  1.2  dibromo- 
cyclohexane.  Both  hydrocarbons  form  different  and  characteristic  di- 
bromides  and  tetrabromides. 


A1-4  cyclohexadiene 
B.-P.  85°-86° 


"Einhorn  &  Meyerburg,  Ber.  27,  2466   (1894). 

"Einhorn  &  Bull,  Ber.  29,  964   (1896)  ;  Ann.  295,  187. 

"Ber.  25,  1840   (1892). 

"«/.  Chem.  Soc.  85,  1410    (1904). 

40  Arm.  302,  30  (1898). 

41 J.  Chem.  Soc.  73,  945   (1898). 

42  Ann.  328,  93,  105   (1903). 

48Z,oc.  cit. 

"Ber.  41,  2479   (1908). 


292       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


A1-3  cyclohexadiene 
B.-P.  81.5° 


Although  the  evidence  of  the  existence  of  the  two  isomeric  hexa- 
dienes  is  quite  clear  some  doubt  as  to  their  constitution  has  been  ex- 
pressed on  account  of  the  fact  that  neither  of  the  hexadienes  shows  the 
exaltation  of  the  molecular  refraction  which  two  conjugated  double 
bonds  were  supposed  always  to  show.  However,  Auwers  has  shown 
that  cyclopentadiene,  which  must  contain  conjugated  double  bonds,  and 
cycloheptadiene,  containing  conjugated  double  bonds,  do  not  show  any 
exaltation  and  the  conjugated  cyclic  trienes  show  only  very  slight  ex- 
altation.45 The  agreement  with  the  calculated  value  of  A1  ^-cyclo- 
hexadiene is  in  fact  within  the  experimental  error,  if  we  accept  the 
more  recent  determinations  of  Harries  46  and  of  Willstatter  and  Hatt.4T 

EMa  EMD 

Harries   0.05  0.09 

Willstatter  and  Hatt 0.00  0.02 

A  similar  discrepancy  between  the  observed  refractivity  and  the 
expected  exalted  value  due  to  conjugation  of  double  bonds  confused 
for  a  time  the  question  of  the  constitution  of  the  substituted  cyclo- 
hexadiene, a-terpinene  (q.  v.).  The  determination  of  the  constitution 
of  such  hydrocarbons  has  been  particularly  difficult  on  account  of  the 
ease  with  which  the  double  bonds  shift  their  positions.  Thus  the  prepa- 
ration of  pure  a-  or  y-terpinene,  a-  or  (3-phellandrene,  and  terpino- 
lene  is  practically  impossible. 

The  cyclohexadienes  show  a  very  marked  tendency  to  oxidize  to 
benzene  (or  its  homologues),  for  example,  the  oxidation  of  the  ter- 
pinenes  to  cymene.  Also  cyclohexadiene  (probably  a  mixture  of  the 
two  isomers)  is  converted  to  benzene  by  dehydrogenation  in  the  pres- 
ence of  nickel  at  the  remarkably  low  temperature  of  ISO0.48  Dilute 
acids  very  frequently  cause  shifting  of  double  bonds  when  a  more 
stable  substance  can  result,  and  a  double  bond  in  a  side  chain  fre- 
quently shifts  to  the  ring.  Thus  2-pheny  1  and  2-propy  1-A2  • 5  • 8 • (9) -men- 

46  For  a  fuller  discussion   of  the  refractivity   of   cyclic  and   acyclic  hydrocarbons 
see  the  chapter  on  physical  properties. 

"Ber.  45,  809  (1912). 

47  Ber.  45,  1647   (1912). 

"Boeseken,  Rec.  trav.  chim.  37,  255   (1918). 


THE  CYCLOHEXANE  SERIES  293 

thatriene  are  quickly  converted  to  the  isomeric  benzene  deriratives  by 
warming  with  3  per  cent  hydrochloric  acid.49 

Conjugated  dienes  react  with  concentrated  sulfuric  acid  with  al- 
most explosive  violence,  with  tar  ^formation  and  reduction  of  the  acid, 
a  behavior  frequently  noted  on  refining  crude  benzene  containing  cyclo- 
pentadiene  and  cyclohexadiene  and  this  energetic  action  is  particu- 
larly marked  when  the  crude  benzene  has  been  manufactured  from 
oil,  as  in  Pintsch  gas  "hydrocarbon"  or  carburetted  water  gas  tar.  Un- 
der the  same  conditions  that  amylene  and  such  simple  defines  give 
good  yields  of.  the  alcohols  (i.  e.,  by  treating  with  ordinary  sulfuric 
acid  in  the  cold  and  diluting  with  water)  the  conjugated  diolefines 
yield  only  tar. 

Cyclohexanol:  This  alcohol  promises  to  become  a  common  com- 
mercial product 50  as  a  result  of  the  development  of  methods  of  cat- 
alytic hydrogenation,  being  readily  prepared  from  phenol.  Cyclohex- 

37° 

anol  has  a  camphor-like  odor,  boils  at  160.9°,  melts  at  23°,  d  -j^- 

0.9397,  nj)  1.46055.51  It  is  sparingly  soluble  in  water  but  is  hygro- 
scopic, a  little  water  lowering  the  freezing-point,  a  eutectic  point  being 
noted  at  — 47.4°,  the  liquid  containing  4.97  per  cent  of  water  at  that 
point.52  The  acetate  resembles  amyl  acetate  and  while  it  has  no  very 
marked  physiological  action,  the  narcotic  action  of  the  vapors  is  about 
three  times  greater  than  the  same  property  of  amyl  acetate.53  The 
naphthylurethane  54  melts  at  139°-140°. 

When  phenol  is  reduced  with  hydrogen  over  active  nickel  at  160°- 
170°,  the  nickel  having  been  reduced  from  the  oxide  at  300°,  the  prod- 
uct is  chiefly  cyclohexanol  together  with  a  little  unchanged  phenol  and 
a  little  cyclohexanone.  Holleman 55  removed  the  cyclohexanone  by 
condensing  it  with  benzaldehyde  in  the  presence  of  alkali.  When  cyclo- 
hexanol is  passed  over  copper,  with  a  little  air,  at  280°  cyclohexanone 

«Klages,  Ber.  40,  2360    (1907). 

60  The  use  of  cyclohexanol  in  soap  is  said  to  enable  one  to  incorporate  solvents 
such  as  benzene,  tetraline.  chlorinated  solvents  and  the  like  in  the  soap  and  also 
facilitates  the  manufacture  of  soaps  containing  phenolic  insecticides.  Its  use  as  a 
solvent  for  rubber  in  reclaiming  rubber  is  mentioned  in  German  Patent  366,146.  Like 
fusel  oil  and  amyl  acetate,  cyclohexanol  and  its  acetate  are  of  value  as  solvents  for 
nitro  cellulose,  such  solutions  being  capable  of  considerable  dilution  with  the  common 
hydrocarbon  solvents,  gasoline,  benzene,  etc.  The  use  of  cyclohexanol  and  cyclo- 
hexanone in  the  manufacture  of  celluloid  has  been  patented  by  Raschig,  German  Pat. 
lT4,yi4  (190o), 

51Auwers,  Ann.  410,  257   (1915). 

"Forcrand,  CAnpt.  rend.  155,  118  (1912). 

"Lehmann,  Chem.  Abs.  1913,  2432. 

"Neuberg,  Bioch.  Z.  27,  339. 

™Rec.  trav.  chim.  24,  19  (1905)  ;  Brochet  [J.  Soc.  Chem.  Ind.  SS,  1031  (1913)] 
used  nickel  and  hydrogen  at  120°-180°  and  10  to  15  kilograms  per  sq.  cm.  pressure. 


294       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

is  produced  in  good  yields.  Sabatier  and  Senderens 56  reduced  phenol 
at  a  higher  temperature  and  obtained  a  mixture  of  cyclohexanone  and 
cyclohexanol,  from  which  they  prepared  cyclohexanol  by  passing  again 
over  the  catalyst  with  hydrogen  at  a  lower  temperature,  140°-150°, 
and  prepared  nearly  pure  cyclohexanone  by  passing  the  mixture  over 
copper  at  330°.  Cyclohexanol  is  readily  oxidized  to  cyclohexanone  by 
chromic  acid,  under  the  same  conditions  that  aliphatic  secondary  alco- 
hols are  oxidized  to  the  corresponding  ketones. 

Cydohexane-1 .2-diol,  melting-point  99°-100°,  is  formed  when 
cyclohexene  is  oxidized  by  cold  dilute  permanganate  in  the  usual  man- 
ner. Cyclohexane-1. 3- diol,57  melting-point  65°,  is  produced  by  the 
catalytic  hydrogenation  of  resorcinol  in  the  presence  of  nickel  at 
130°.  It  is  easily  soluble  in  water  and  alcohol,  does  not  reduce  Feh- 
lings'  solution  or  give  a  color  with  ferric  chloride.  Cyclohexane-1 .2.3- 
triol  was  also  obtained  by  the  catalytic  hydrogenation  of  pyrogallol^ 
the  triol  forming  very  hygroscopic  crystals  melting  at  67°.  Cyclo- 
hexane-1.3.5-diol,  made  by  reducing  phloroglucine  with  sodium  amal- 
gam, melts  at  184°.  Cyclohexane-1 .4- diol,  also  called  quinite  can  be 
obtained  by  catalytic  hydrogenation  of  hydroquinone  and  was  also 
prepared  by  Baeyer  by  reducing  cyclohexane-1.4-dione  with  sodium 
amalgam.  It  was  named  quinite  on  account  of  its  relation  to  benzo- 
quinone,  which  it  yields  when  oxidized  by  chromic  acid.  Two  other 
hydroxyl  derivatives  of  cyclohexane  may  be  mentioned  on  account  of 
their  interest  to  biochemistry,  i.  e.,  quercite,  cyclohexane-1.2.3.4.5- 
pentol,  and  inosite,  cyclohexane-1.2.3.4.5.6-hexol.  Quercite  is  known 
in  two  forms  [<x]D  +  24.16°,  melting-point  235°,  and  [a]D  —73.9°, 
melting-point  174°.  The  chemical  behavior  of  quercite  and  inosite  is 
very  closely  parallel  to  the  behavior  of  sorbite,  rhamnite,  etc.  Both 
substances  have  been  known  for  a  long  time  and  their  chief  interest 
in  connection  with  a  discussion  of  the  chemistry  of  the  hydrocarbons 
is  that  ring  closing  makes  such  slight  differences  in  their  chemical 
properties  as  compared  with  the  alcohols  of  the  methyl  pentose  and 
hexose  series.  Quercite  yields  a  pentacetyl  derivative  melting  at  125°, 
an  explosive  pentanitrate  and  an  amorphous  pentaphenyl  carbamate. 
Inosite  yields  a  hexacetate  melting  at  212°  and  a  very  explosive  hex- 
anitrate.  A  monomethyl  ether  of  inosite  has  been  reported  in  a  caout- 
chouc (gutta-percha  ?)  from  Borneo  and  a  dimethyl  ether  in  another 

"Compt.  rend.  137,  1025   (1903). 

"Sabatier  &  Mailhe,  C&mpt.  rend.  1*6,  1193   (1908). 


THE  CYCLOHEXANE  SERIES 


295 


specimen  of  caoutchouc.58  The  resin  of  the  California  pine,  Pinus 
lambertiana,  also  contains  a  monomethyl  ether  of  d-inosite.59  This 
ether,  pinite,  has  been  found  in  other  plant  secretions,  tastes  very 
sweet,  melts  at  186°,  and  following  the  general  behavior  of  such  ethers, 
is  readily  split  by  warming  with  concentrated  hydriodic  acid,  to  methyl 
iodide  and  the  alcohol. 

THE  PHYSICAL  PROPERTIES  AND  LITERATURE  REFERENCES  OP  THE  CYCLOHBXANOLS 

20° 

Name                                  B.-P.  d  4° 

Cyclohexanol  160.9  0.949 

Methylcyclohexanol-(l)    ..  156.    -158.  °            0.924 

Methylcyclohexanol-(2)    ..  168.  0.928 

Methylcyclohexanol-(3)    ..  174.  0.917 

Methylcyclohexanol-(4)    ..  173.  0.919 

1.3-Dimethylcyclohexanol-(l).  169.  0.903 

1.4-Dimethylcyclohexanol-(l).  170.  0.909 

2.2-Dimethylcyclohexanol-(l).  177.  0.922 

33-Dimethylcyclohexanol-(l).  185.  0.909 

4.4-Dimethylcyclohexanol-(l).  186.  0.925 

2.4-Dimethylcyclohexanol-(l).  176.5  0.908 

2.5-Dimethylcyclohexanol-(l).  178.5  0.904 

2.6-Dimethylcyclohexanol-(l).  174.5-175.5°  0.924 

3.4-Dimethylcyclohexanol-(l).  189.  0.904 

3.5-Dimethylcyclohexanol-(l).  187.  0.898 

1.3.5-Trimethylcyclohexanol-(l)  181.  0.886 

3.3.5-Trimethylcyclohexanol-(l)  200.  0.897 

2.2.5-Trimethylcyclohexanol-U)  187.  0.900 
2.2.6.6-Tetramethylcyclohexanol- 

(1)    195.  M97.  °           0.897 

2.2.5.5-Tetramethylcyclohexanol- 

(1)   .  202.  °  0.902 


SO0 

nD 

References 

1.4659 

1 

1.4585 

1 

1.463 

2 

1.458 

3 

1.458 

4 

1.455 

5 

1.457 

5,6 

1.464 

7 

1.459 

8 

1.463 

9 

1.4562 

10 

1.4532 

10 

1.4628 

11 

1.4562 

10 

1.453 

12 

1.453 

13 

1.453 

12 

1.459 

14 

1.4537 

15 

1.462 

16 

1  Zelinsky,  Ber.  34,  2800  (1901) ;  Auwers,  Ann.  410,  309  (1915). 

2  Wallach,  Ann.  329,  375  (1903) ;  Murat,  Chem.  Zentr.  1909  (2),  851. 

3  Zelinsky,  Ber.  30,  1534  (1897);  Haller  and  March,  Chem.  Zentr.  1905  (2), 

325;  Sabatier  and  Mailhe,  Chem.  Zentr.  1905  (1),  742. 

4  Sabatier  and  Mailhe,  Chem.  Zentr.  1907  (1),  1096;  Auwers,  Ann.  410,  309 

(1915). 

5  Sabatier  and  Mailhe,  Chem.  Zentr.  1905  (2),  483. 

6  Wallach,  Ann.  396,  266  (1913). 

7  Auwers  and  Lange,  Ann.  401,  319  (1913);  Meerwein,  Ann.  405,  144  (1914). 

8  Perkin,  Sr.,  J.  Chem.  Soc.  87,  1493  (1905);  Auwers  and  Lange,  Ann.  401, 

314  (1913). 

9  Auwers  and  Lange,  loc  cit. 

10  Sabatier  and  Mailhe,  Chem.  Zentr.  1906  (1),  1248. 

11  Haller,  Chem.  Zentr.  1913  (2),  1144. 

12  Knoevenagel,  Ann.  297,  182  (1897);  Auwers,  Ann.  410,  311  (1915). 

13  Wallach  and  Schlubach,  Ann.  396,  284  (1913). 

14  Wallach,  Ann.  329,  87  (1903);  Auwers,  Ber.  41,  1814  (1908). 

15  Haller,  Chem.  Zentr.  1913  (2),  41. 

16  Auwers  and  Lange,  Ann.  409,  178  (1915). 


"Flint  &  Tollens,  Ann.  27*,  288   (1893). 
"Wiley,  J.  Am.  Chem.  Soc.  13,  228   (1891). 


296       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

A  great  many  alkyl  derivatives  of  cyclohexanol  are  known,  the 
simpler  ones  being  readily  made  by  catalytic  hydrogenation  of  the 
cresols,  by  the  Grignard  reaction  on  cyclohexanone  and  other  well- 
known  methods.  As  in  the  aliphatic  series  the  secondary  alcohols  are 
not  easily  decomposed  to  unsaturated  hydrocarbons  but  tertiary  alco- 
hols of  the  type 


yield  unsaturated  hydrocarbons  very  readily. 

Cyclohexanone:  On  account  of  the  very  great  value  of  this  ke- 
tone  as  a  material  for  the  synthesis  of  a  very  large  number  and  va- 
riety of  hydrocarbons,  it  will  be  briefly  described.  Its  best  method  of 
preparation  has  already  been  described  in  connection  with  cyclo- 
hexanol. Its  chemical  behavior  closely  parallels  that  of  the  aliphatic 

"1  f\  Q° 

ketones.    Pure  cyclohexanone  boils  at  156.6°-156.8°  d      '     0.9503,  n^ 

1. 45261. 60  It  may  be  characterized  by  the  phenylhydrazone  melt- 
ing at  74°-77°  and  the  condensation  products  with  benzaldehyde 
C6H5CH  =  (C6H80)  melting  at  53°  and  the  dibenzylidene  compound 
C6H5CH  =  (C6H60)  —  CH.C6H5  melting  at  1170.61  The  ketone,  like 
cyclopentanone,  is  condensed  by  sodium  ethylate  or  by  gaseous  hydro- 
gen chloride  to  cyclohexylidenecyclohexanone  and  a  dicyclohexylidene- 
cyclohexanone.  The  ring  is  not  easily  broken  but  in  direct  sunlight 
in  dilute  alcohol  solution  capronic  acid  and  A5  hexene  aldehyde  are 
formed,  and  the  oxime  is  converted  by  concentrated  sulfuric  acid  to 
the  iso-oxime,  or  e-caprolactam.  With  an  excess  of  bromine  in  the 
cold  it  yields  a  tetrabromide  melting  at  119°,  but  when  brominated  hot 
the  chief  product  is  2.4.6-tribromophenol.62 

Methylcyclohexane  occurs  in  Russian 63  and  Galician  64  petroleum. 
Galician  petroleum  appears  to  be  midway  between  Russian  petroleum 
and  oils  of  the  Pennsylvania  type.  The  presence  of  methylcyclohexane 
in  Russian  petroleum  was  regarded  as  "probable"  by  Young.  It  also 

«°Auwers,  Ann.  410,  257   (1915). 
61  Wallach,  Goettingen  Nachr.  1907,  402 ;  Ber.  40,  71. 
^Bodroux  &  Taboury,  Compt.  rend.  154,  1509   (1912). 

"Milkowski,  J.  Russ.  Phys.-Ohem.  Soc.  11,  37  (1885);  Zelinsky,  Ber.  SO,  1532 
(1897). 

«« Skowronski,  Chem.  Al».  1920,  3523. 


THE  CYCLOHEXANE  SERIES  297 

occurs  in  rosin  spirit 65  and  can  readily  be  prepared  by  the  catalytic 
hydrogenation  of  toluene.  Reduction  of  cycloheptanol  by  heating  with 
concentrated  hydriodic  acid  causes  a  rearrangement  of  the  carbon 
structure  giving  methyl  cyclohexane  as  the  reduction  product. 

When  treated  with  bromine  and  aluminum  bromide  the  principal 
product  is  pentabromotoluene,  melting  at  282°,  and  this  fact  can  be 
used  for  detecting  the  presence  of  methyl  cyclohexane  in  gasoline, 
after  proper  fractional  distillation.  When  methylcyclohexane  is  ni- 
trated by  Konowalow's  method  using  nitric  acid,  Sp.  Gr.  1.20,  the 
yield  of  nitro  derivatives  is  about  58  per  cent,  but  Nametkin66  re- 
ports that  nitration  by  aluminum  nitrate  gives  about  72  per  cent  of 
nitrated  products.  The  tertiary  nitro  derivative  may  be  separated 
from  the  primary  and  secondary  derivatives  by  the  solubility  of  the 
latter  two  types  in  alkali.  1 . 1-Nitromethylcyclohexane  is  a  liquid  dis- 

0° 
tilling  at  109-°110°  (40  mm.),  d-wl.Q547  and  may  be  reduced  by  tin 

and  hydrochloric  acid  to  the  amine  boiling-point,  143°    (744  mm.). 

0° 

The  1.3-nitromethylcyclohexane  distills  at  119°-120°  (40  mm.),  d-^ 

1.0547;  cyclohexylnitromethane,  C6HU.CH2N02,  is  also  formed.  Oxi- 
dation of  methylcyclohexane  by  nitric  acid  yields  a  mixture  of  adipic, 
succinic,  oxalic,  glutaric  and  pyrotartaric  acids. 

The  chlorination  of  methylcyclohexane  yields,  of  the  monochlo- 
rides,  about  60  per  cent  l-methyl-3-chlorocyclohexane  and  about  40 
per  cent  of  the  1 . 2-derivative.  This  was  shown  by  forming  the  mag- 
nesium derivatives  with  the  monochlorides  passing  oxygen  into  the 
ethereal  Grignard  solution,  and  examining  the  resulting  alcohols. 
Cyclohexylmethyl  chloride,  C6Hn.CH2Cl,  made  from  the  correspond- 
ing carbinol,  boils  at  166°  (760  mm.)  without  appreciable  decompo- 
sition; 2-chloromethylcyclohexane  boils  at  156°  with  slight  decompo- 
sition; 3-chloromethylcyclohexane  distills  at  157°  and  4-chloromethyl- 
cyclohexane  distills  at  158°,  also  decomposing  appreciably.67 

Methyl  Cyclohexenes:  Of  the  three  methyl  cyclohexenes  A1-methyl 
cyclohexene  is  the  most  stable,  the  other  two  isomers  being  readily 
converted  to  the  A1  hydrocarbon  by  heating  with  dilute  acids.  The  A1 
hydrocarbon  is  also  present  in  the  mixture  of  hydrocarbons  obtained 
by  decomposing  methylcyclohexanol-(3)  or  methylcyclohexanol- (4) 
with  phosphorus  pentoxide  or  zinc  chloride.  Decomposition  of  1.1  or 

•Ann.  cMm.  phys.   (6)  1,  229  (1884). 

MJ.  Rugs.  Phvs.-Chem.  Soc.  kt,  691   (1910). 

"  Sabatier  &  Mailhe,  Compt.  rend.  HO,  840  (1905). 


298       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

1 . 2-methylcyclohexanol  yields  the  A1  hydrocarbon.  Wallach  68  pre- 
pared it  by  treating  cyclohexanone  with  methyl-magnesium  iodide  and 
decomposing  the  tertiary  alcohol  by  zinc  chloride.  Its  boiling-point, 
111°-1120,  is  several  degrees  higher  than  the  isomeric  methenecyclo- 
hexane  prepared  by  Wallach  by  distilling  and  decomposing  cyclo- 
hexene  acetic  acid.  The  A1  hydrocarbon  yields  a  glycol,  by  per- 
manganate oxidation,  melting  at  67°.  When  1.2  methylcyclohexanol 
is  decomposed  by  Ipatiev's  method,  passing  the  vapors  over  heated 
alumina  at  350°,  a  mixture  of  methylcyclohexenes,  distilling  from 
96°-100°,  is  formed,  but  when  a  mixture  of  alumina  and  copper  oxide 
is  used,  the  reaction  takes  place  smoothly  at  240°  and  the  product  is 
nearly  pure  A^methylcyclohexene.69  By  condensing  cyclohexanone 
and  bromoacetic  ester  in  the  presence  of  zinc,  Wallach 70  made  cyclo- 
hexanolacetic  acid  which  on  decomposing  with  bisulfate  or  P205  yields 
mainly  A1-cyclohexene-acetic  acid  but  by  heating  with  acetic  anhy- 
dride yields  mainly  A1(7)-cyclohexeneacetic  acid,  a  reaction  frequently 
employed  for  the  synthesis  of  methene  derivatives  in  the  cyclohexane 
and  cyclopentane  series.  Distillation  of  the  unsaturated  acids  yields 
the  hydrocarbons,  as  indicated  below, 


HCO£H 


Methenecyclohexane7i  boils  at  103°,  d19  0.8020,  nD  1.4499.     It 
readily  absorbs  hydrogen  chloride,  forming  an  unstable  chloride  boiling 

88  Ann.  359,  287   (1908). 

*°B&r.  43,  3383   (1910)  ;  J.  Russ.  Phys.-Chem.  Soc.  U,  1675   (1913). 

™Ann.  353,  288   (1906). 

"Wallach,  Ann.  365,  262   (1909)  ;  Favorsky  &  Borgmann,  Ber.  40,  4863. 


THE  CYCLOHEXANE  SERIES 


299 


at  151°-152°.  It  is  easily  converted  to  A^methylcyclohexene  by  alco- 
holic sulfuric  acid  and  on  hydrating  by  dilute  sulfuric  acid  yields  the 
tertiary  alcohol  1 . 1-methylcyclohexanol.  Permanganate  oxidation 
yields  cyclohexanone  and  a  glycol  melting  at  67° -77°.  Its  nitroso- 
chloride  may  be  converted  into  the  nitrolpiperidide,  useful  for  identi- 
fication or  HC1  may  be  removed  by  heating  with  sodium  acetate  in 
acetic  acid  to  give  an  aldoxime  (a  very  general  reaction  of  nitroso- 
chlorides,  giving  an  aldoxime  or  ketoxime).  Hydrolysis  of  the 
aldoxime  yields  A^cyclohexene  aldehyde,  an  aldehyde  having  an  odor 
greatly  resembling  benzaldehyde.  Since  these  reactions  are  widely 
applicable  and  have  in  fact  been  frequently  employed,  they  are  noted 
here, 


HO 


The  glycol  is  readily  converted  to  the  saturated  cyclohexyl  aldehyde 
by  the  action  of  dilute  acids,  also  a  very  general  reaction,  and  having 
its  parallel  in  the  behavior  of  the  1.2-glycols  of  the  aliphatic  series 
CH^OH  CHO 

OH 


Unlike  benzaldehyde,  cyclohexyl  aldehyde  polymerizes  very  easily  to 
the  dimeride  (C7H120)2  and  with  acids  the  substance  (trimeride  ?) 
(C7H120)8  is  formed. 

&*-Methylcyclohexene,  boiling-point  103°,  may  be  obtained  by 
heating  and  decomposing  the  acid  phthalic  ester  or  methyl  xantho- 
genate  of  methylcyclohexanol(3)  or  by  decomposing  the  iodide  by 
alcoholic  caustic  potash  or  dimethyl  aniline.  From  optically  active 
methylcyclohexanol  (3)  Zelinsky 72  obtained  an  optically  active  hydro- 
carbon by  decomposing  the  iodide.  The  hydrocarbon,  the  constitu- 

"Ber.SS,  2488  (1902). 


300       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

tion  of  which  was  not  proven,  varied  according  to  the  method  of 
preparation,  the  hydrocarbon  obtained  by  caustic  potash  having  the 
highest  rotation, 

(1)  by  alcoholic  KOH  —  boiling-point  103°-103.5°,  [a]D  +  81.4° 

(2)  by  dimethyl  aniline,  boiling-point  105°-106    °,  [<x]D  +48.3° 

When  A3-methylcyclohexene  is  treated  with  sulfuric  acid  (1  volume 
water  to  two  volumes  of  acid)  the  principal  product  is  the  dimeride, 
C14H24,  and  more  dilute  acid  (1:1  by  volume)  converts  it  to  a  mixture 
of  the  A1  and  A2  isomers  and  alcohols,  among  which  methylcyclohex- 
anol(3)  were  identified.73 

1.1  Dimethylcyclohexane:  This  hydrocarbon  has  been  synthesized 
by  Crossley  and  Renouf,74  from  1  .  1-dimethyldihydroresorcin.  Zelin- 
sky  and  Lepesckin75  had  prepared  a  hydrocarbon  which  they  con- 
sidered to  be  1  .  1-dimethylcyclohexane  from  laurolene  and  isolaurolene 
but  the  work  of  Crossley  and  Renouf  shows  that  Zelinsky's  conclusions 
were  incorrect.  Crossley  and  Renouf  treated  1  .  1-dimethylcyclohex- 
anol(3)  with  hydrogen  bromide  in  acetic  acid  and  reduced  the  bromide 
with  zinc  dust  in  acetic  acid  to  1  .  1-dimethylcyclohexane.  The  hydro- 
carbon is  stable  to  bromine  and  permanganate  in  the  cold  and  is  slowly 
oxidized  by  fuming  nitric  acid  to  P(3-dimethyladipic  acid.  When 
the  above  bromide  (3)  is  treated  with  alcoholic  caustic  potash 
1  .1  -dimethyl-  h?-cydohexene  is  formed,  apparently  not  contaminated 
with  the  AMsomeride.  The  unsaturated  hydrocarbon  has  a  turpentine 
like  odor  and  yields  (3|3-dimethyladipic  acid  on  oxidation  by  perman- 
ganate. The  physical  properties  of  the  two  hydrocarbons  are  as 
follows, 

*-<•• 


1  .  1-dimethylcyclohexane    ...............          102°  0.7864 

1  .  l-dimethyl-A3-cyclohexene  ............     117°-117.5°  0.8040 

Zelinsky's  hydrocarbon  boils  at  111.5°-1140,  d—  0.7686,  and  on  oxida- 

tion does  not  yield  |3|3-dimethyladipic  acid.  The  physical  properties 
of  1  .  1-dimethylcyclohexane  prepared  from  1  .  1-dimethylcyclohexane- 
3-one,  by  reduction  to  the  alcohol,  and  conversion  of  the  latter  to  the 

"  Markownikow,  J.  Rus8.  Phys.-C'hem.  Soc.  S5,  1049  (1903). 

™J.  Chem.  Soc.  87,  1487  (1905)  ;  89,  27  (1906). 

"Ann.  519,  303  (1901)  ;  J.  Ruse.  Phys.-CJiem.  Soc.  S3,  549  (1901). 


THE  CYCLOHEXANE  SERIES  301 

unsaturated  hydrocarbon  followed  by  catalytic  hydrogenation  were, 

90°  20° 

boiling-point  118.5°,  d-^-0.7825,  n  —-1.4289.76 

Zelinsky  and  Lepeschkin77  later  confirmed  the  work  of  Crossley  and 
Renouf  by  the  synthesis  of  1 . 1-dimethylcyclohexane  in  another  man- 
ner (from  (3-methyl-A0-heptone-l;-one)  and  noted  the  following:  boil- 

16°  16° 

ing-point  119-2°-119.7°,  d  —  0.7843,  n—  1.4320.  When  1. 1-dime- 
thylcyclohexane is  brominated  in  the  presence  of  aluminum  bromide 
one  of  the  methyl  groups  goes  to  the  para  position,  resulting  in  a 
para-xylene  derivative. 

Auwers78  has  prepared  a  series  of  methyl  derivatives  of  cyclo- 
hexane.  The  method  of  preparation  most  frequently  employed  was 
the  catalytic  hydrogenation  of  phenols,  conversion  of  the  resulting 
secondary  alcohols  to  iodides  and  reduction  of  the  latter  by  zinc  dust 
and  acetic  acid.  Also  tertiary  alcohols,  formed  by  treating  cyclo- 
hexanone  derivatives  with  magnesium  methyl  iodide,  were  converted 
to  the  corresponding  chlorides  by  the  action  of  phosphorus  trichloride 
and  the  resulting  chlorides  reduced  to  the  saturated  hydrocarbon  by 
sodium  in  moist  ether.  A  summary  of  the  physical  properties  of  the 
methyl  derivatives  of  cyclohexane,  as  determined  by  Auwers  is  given 
in  the  following  table. 

ALKYL  DERIVATIVES  OF  CYCLOHEXANE: 

I.  METHYL  DERIVATIVES. 
Name  Structure  B.-P*       d  ~-       n^- 

Cyclohexane  <^"~          \  80.5°        0.778        1.427 

Methylcyclohexane  ^  ^>— CS»  101.  °        0.771        1.423 

y v    yCH» 

1.1-dimethylcyclohexane  {  }\  120.  °        0.781        1.430 


1.2-dimethylcyclohexane  < V-CH,  123.  °        0.779        1.429 


rated*  mor^^d^^rom^rch^the?.6  ^^  ^Te&SG8  **  ^  methyl  groups  are 


&  Ssorokina,  Chem.  Ztg.  37,  725  (1913). 

"  J.  RUBS.  Phys.-Chem.  Soc.  45,  613   (1913). 
"Ann.  4^0,  88   (1919). 


302       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

CH, 


1.3-dimethylcyclohexane  " 
1.4-dimethylcyclohexane 

1 . 1 .3-trimethylcyclohexane 


1.2.4-trimethylcyclohexane     C 


1.2.3-trimethylcyclohexane 80 
1 .3.5-trimethylcyclohexane 


1 .2.4.5-tetramethylcyclohex- 
ane 


119.  ° 

120.  ° 


0.771 
0.769 


1.425 
1.424 


138.  °        0.790       1.436 


140. 


0.778       1.429 


149.6°-150° 


138.  °        0.772 


1.429 


161.  °        0.785        1.434 


The   boiling-points   and  densities   of   other   alkyl   derivatives   of 
cyclohexane  are  given  in  the  following  table. 

ALKYL  DERIVATIVES  OF  CYCLOHEXANE  II. 
Name 


D   D        r>  20°  Ref 

B.-P.       Density f -^ 


1.2-Methylethyl  cyclohexane    

151° 

0.784 

i 

n.Propylcyclohexane    

156° 

0.7865 

a 

Tertiarybutylcyclohexane                                    . 

166°-167° 

1/>o 

08305^^- 

4 

1.3-Methylethylcyclohexane   

145°-146° 

0.8320 

6 

1.3-Methylpropylcyclohexane    

164°-165° 

5 

1.2-Methylisopropylcyclohexane  [o-menthane]    ... 

171° 

21° 
0.8135-^- 

6 

1.3-Methylisopropylcyclohexane  [m-menthane]   .  . 

166M670 

94° 

0.7965^- 

6 

"Zelinsky,  Ber.  35,  2677  (1902),  gives  the  following,  boiling-point  119.5-120°,  d~ 

0.7661.     Zelinsky  prepared  the  hydrocarbon  by  converting  1.3-dimethyl  cyclohexanol  (1) 
to  the  iodide  and  reducing  it  with  zinc  in  acetic  acid. 
•oTreppmann  &  Krollpfeiffer,  Ber.  48,  1226  (1915). 


THE  C  YCLOHEXANE  SERIES  303 

'    25° 

1.4-Methylisopropylcyclohexane  [p-menthane]    ...    167°-168°        0.8028-^r       6 

2-Cyclohexyl-2-methylbutane  0 

CeHu.C(CH3)2C2H5 191M920        0.8226^-       4 

2-Cyclohexyl-2-methylpentane    206°-207°        0.8372^       4 

3-Cycloliexyl-3-methylpentane    207°-208°        0.8310^-       4 

3-Cyclohexyl-3-ethylpentane   222°-223°        05388^       4 

in* 
2-Cyclohexyl-2.4-dimethylpentane    220°-221°        0.8304-^-       4 

1  r»O 

3-Cyclohexyl-3-methylhexane   224°-226°        0.8406  -^-       4 

17° 
l-Methyl-2-isoamylcyclohexane    204°  0.812-^5-         7 

1  Sabatier  and  Senderens,  Compt.  rend.  132,  210,  556  (1901). 

2  Murat,  Ann.  chim.  phys.  (8)  16,  108  (1909). 

3  Kursanoff,  Ber.  34,  2035. 

4  Halse,  J.  prakt.  Chem.  (2)  92,  40  (1915).    The  hydrocarbons  described  by 

Halse  were  made  by  Willstatter's  method  of  catalytic  hydrogenation. 

5  Mailhe  and  Murat,  Bull.  soc.  chim.  7,  1083  (1910).    Zelinsky,  Ber.  35,  2677 

(1902),  gives  the  boiling-point  148°-149°,  d1^  0.7896. 

6  Sabatier  and  Murat,  Compt.  rend.  156,  184. 

7  Murat,  Ann.  chim.  (8)  16,  108  (1909). 

Of  the  hydrocarbons  noted  in  the  above  tables,  cyclohexane,  methyl- 
cyclohexane,  1 . 3-dimethylcy  clohexane  and  1 . 3 . 4-trimethy  Icy  clo- 
hexane  have  been  reported  in  the  lighter  fractions  of  Russian  petro- 
leum, and  the  methyl,  propyl,  1 . 3-dimethyl  and  1.4-dimethyl 
derivatives  have  been  reported  in  rosin  oil.  The  method  of  identify- 
ing alkyl  cyclohexanes  by  brominating  in  the  presence  of  aluminum 
bromide  to  benzene  derivatives  which  are  supposed  to  retain  the  alkyl 
groups  in  the  same  relative  positions  as  they  occurred  in  the  original 
cyclohexane  hydrocarbon,  is  open  to  the  objection  that  profound 
alteration  of  the  carbon  structure  of  the  hydrocarbon  has  frequently 
been  observed  in  the  presence  of  aluminum  bromide;  thus  1.1-dime- 
thy  Icy  clohexane  gives  a  bromide  derivative  of  para-xylene.  The  same 
objection  could  be  made  to  an  attempt  to  convert  the  alkyl  cyclohexane 
to  the  corresponding  alkyl  benzenes  by  dehydrogenation  over  nickel  at 
about  300°.  In  view  of  the  extreme  difficulty  of  separating  such 
hydrocarbons  from  petroleum  by  fractional  distillation,  to  which  diffi- 
culty Young  has  called  attention,  and  the  equally  great  difficulties  and 
uncertainties  of  identifying  them  by  chemical  means  (conversion  to 
benzene  derivatives  or  oxidation  to  known  acids,  etc.),  it  is  quite 


304       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

probable  that  many  of  the  cyclic  hydrocarbons  reported  to  have  been 
identified  in  Russian  petroleum  have  been  so  reported  on  faulty  or 
insufficient  evidence. 

Although  a  fair  number  of  alkyl  derivatives  of  cyclohexane  are 
known,  very  little  is  known  of  their  chemical  behavior;  for  example, 
to  concentrated  sulfuric  acid,  nitric  acid,  chromic  acid  and  the  like. 
Even  in  the  case  of  the  menthanes,  it  is  not  known  in  what  positions 
bromine  enters  on  bromination  and  whether  or  not  the  tertiary  hydro- 
gen atoms  are  reactive  to  sulfuric  acid  or  are  easily  oxidized.  In  view 
of  the  very  large  losses  which  result  on  treating  petroleum  distillates 
with  sulfuric  acid,  it  would  be  desirable  to  know  whether  the  different 
types  of  substituted  cyclohexanes,  bicyclic  and  polycyclic  hydrocar- 
bons of  different  types,  saturated  in  the  sense  that  no  double  bonds 
are  present,  are  resistant  to  air  oxidation,  resinification,  destruction 
by  concentrated  sulfuric  acid,  etc. 

The  Substituted  Cyclohexenes  follow  very  generally  the  chemical 
behavior  noted  in  the  so-called  terpene  series.  Only  in  comparatively 
recent  years  has  it  been  realized  that  the  chemistry  of  these  hydro- 
carbons occurring  in  nature  cannot  be  dissociated  in  any  way  from 
the  chemistry  of  the  simple  derivatives  of  cyclopentane,  cyclohexane 
and  cycloheptane.  The  boiling  points,  densities  and  refractive  indices 
of  a  number  of  unsaturated  hydrocarbons  of  this  series  are  given  in 
the  following  table. 


THE  CYCLOHEXANE  SERIES 


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306       CHEMISTRY  OF  THE  NON-BENZEN01D  HYDROCARBONS 


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THE  CYCLOHEXANE  SERIES 


307 


Wallach81  tabulates  the  physical  properties  of  a  series  -of  cyclo- 
hexane  derivatives  each  of  which  contains  a  semicyclic  double  bond, 
as  follows, 


Boiling-point    .         ..  102.° 
d  ...................        0.8025 

MD     ..............  ...      32.15 

MD    (calc.)  .........  31.83 


<(  ^= 

Boiling-point    ....  137.M38.0 

d  ...............        0.823 

MD    ............  36.82 

(calc.)  .....  36.43 


123.°-124.° 
0.798 
36.95 
36.43 


122.M230 
0.7925 
36.93 
36.43 


CH, 


153.0 

0.813 
41.65 
41.03 


156.° 

0.8125 
41.65 
41.03 


CH, 


Boiling- 

point 

d   ..... 


_  ,  _  , 

>=CH.C2H.     <        >=CH.C2H6  CH^       V=CH.CaH, 


Mr>(calc 


157.M58.0 
0.821 
41.60 
)  41.03 


CH, 


170.°-173.° 
0.814 
46.35 
45.64 

CH, 


172.°-174.° 
0.815 
46.28 
45.64 


Boiling- 

point     160.M61.0 
d    .....        0.836 
MD    ..       41.56 
MD  (calc.)  41.03 


CH, 


173.°-175.° 
0.825 
46.25 
45.64 


172.°-174.° 
0.831 
45.88 
45.64 


1  .2-Dimethyl-^-Cyclohexene  is  of  special  interest  since  Meer- 
wein82  discovered  that  it  is  smoothly  formed  by  the  dehydration  of 
the  cyclopentane  derivative  1-methyl-l-a-hydroxyethylcyclopentane. 
CH2  —  CH2  CH3  CH2  —  CH2  —  C  —  CH3 

I  >C<  -  >     |  II 

CH2  —  CH2          CH  (OH)  .  CH3  CH2  —  CH2  —  C  —  CH8 

The  hydrocarbon  is  also  formed  by  the  dehydration  of  1  .  2-dimethyl- 
cyclohexanol(l).  It  is  therefore  readily  prepared  from  methylcyclo- 
hexane-2-one  by  treating  with  methyl-magnesium  iodide  and  dehy- 
drating the  resulting  alcohol.  The  nitrosochloride  is  bluish  in  color, 
easily  volatile  with  steam  and  melts  at  58°-60°.  It  yields  a  dibro- 
mide  C8H14Br2  melting  at  154°-156°  and  by  oxidation,  the  glycol 
melting  at  38°-39°.83 

«  Ann.  360,  34. 

"Ann.  417,  255   (1918). 

»  Wallach,  Ann.  S96,  278  (1913). 


308       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


Ethylidenecyclohexane  has  been  synthesized  by  the  Reformatsky 
synthesis,  condensing  cyclohexanone  and  <x-bromopropionic  acid  and 
decomposing  the  resulting  cyclohexanolpropionic  acid 

CH2  — CH2 

/  \        OH 

CH2  C< 

\  /        CH(CH3).C02H. 

CH2  — CH2 

in  the  usual  manner.  The  nitrosochloride  melts  at  132°. 88a  Following 
the  general  rule  that  on  treating  with  alcoholic  sulfuric  acid  semi- 
cyclic  double  bond  shifts  to  the  ring,  ethylidenecyclohexane  when  so 
treated  yields  e^%^-A1-cyclohexene.  The  latter  hydrocarbon  is  more 
readily  prepared  by  treating  cyclohexanone  with  ethyl-magnesium 
bromide  and  dehydrating  the  resulting  tertiary  alcohol  in  the  usual 
manner.  Propylidenecyclohexane  is  similarly  prepared  and  also  re- 
arranges readily  to  propyl-A^cyclohexene.84 

The  hydrocarbon  1.3-dimethyl-A3-cyclohexene,  noted  in  the  above 
tables,  is  identical  with  the  so-called  "tetrahydro-meta-xylene"  ob- 
tained by  condensing  methylheptenone.  It  yields  a  nitrosochloride 
and  a  characteristic  nitrolpiperidide  melting  at  130°-131°.85 

1.4  Di-isopropylcyclohexane:  Several  unsaturated  hydrocarbons 
having  the  carbon  structure  of  di-isopropylcyclohexane  have  recently 
been  prepared  by  Bogert  and  Harris86  by  well-known  methods  of 
synthesis.  When  the  esters  of  the  hydrogenated  terephthalic  acids 
were  treated  with  methyl-magnesium  iodide  the  glycols  were  not 
obtained,  these  passing  immediately  into  the  hydrocarbons. 

CH,.     >H,  CH          CH, 


CH 


"•Wallach,  Ann.  589,  189  (1912). 
"Wallach,  Ann.  360,  56. 
"Wallach,  Ann.  896,  264    (1913). 
88  J.  Am.  Chem.  8oc.  41,  1678  (1919), 


THE  CYCLOHEXANE  SERIES 


309 


The  hydrocarbon  I,  1.4-di-isopropenyl-A1>4-cyclohexadiene,  melts  at 
117°-117.5°,  yields  an  oily  tetrabromide  and  also  a  crystalline  tetra- 
bromide  melting  at  107°-109°.  When  it  was  attempted  to  add  more 
bromine,  substitution  and  evolution  of  hydrobromic  acid  occurred 
similar  to  the  behavior  of  A3-8(9)-p-menthadiene  noted  by  Perkin, 
which  adds  smoothly  only  two  atoms  of  bromine  supposedly  on  ac- 
count of  the  fact  that  the  two  double  bonds  are  in  the  conjugated 
position.  Bogert  and  Harris  regard  their  liquid  and  crystalline  tetra- 
bromides  as  cis  and  trans  isomers  of  the  substance 


CHd—  C—  CH,Br 


The  refractive  index  of  the  hydrocarbon  was  determined  in  benzene 
and  in  chloroform  solutions,  using  Eisenlohr's  values,  and  an  exalta- 
tion of  the  molecular  refraction,  due  to  the  two  conjugated  double 
bond  systems  of  3.776,  was  found.  Bogert  and  Harris  note  that  almost 
the  same  exaltation  of  the  molecular  refraction  was  noted  in  the  case 
of  1.4-disopropenylbenzene,  i.e.,  3.841,  which  they  believe  points  to  a 
structure  analogous  to  Dewar's  structure  for  styrene, 


310       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

CH— C=CHZ 


CH=C-CH3 


The  values  obtained  for  the  magnetic  rotatory  power  of  p-di-isopro- 
penyl-benzene,  however,  point  to  a  Kekule,  not  a  Dewar  structure. 

Cantharene,  a  hydrocarbon  obtained  by  the  decomposition  of 
cantharidene,  has  been  synthesized  by  Haworth  87  from  1-methyl-A1- 
cyclohexene  in  the  following  manner.  The  nitrosochloride  of  the 
methylcyclohexene  was  heated  with  sodium  acetate  in  acetic  acid, 
removing  hydrogen  chloride  in  the  usual  manner  and  by  hydrolyzing 
the  resulting  unsaturated  oxime  l-methyl-A6-cyclohexene-2-one  was 
obtained.  A  methyl  group  was  introduced  by  means  of  methyl- 
magnesium  iodide  and  the  resulting  tertiary  alcohol  was  decomposed 
by  heating  with  8  per  cent  oxalic  acid. 


Cantharenol  Cantharene 

Monocyclic  Sesquiterpenes :  The  name  "sesquiterpene"  has  been 
employed  for  a  number  of  hydrocarbons  of  the  formula  C15H24  occur- 
ring in  essential  oils.  Semmler  has  recently  made  several  hydrocar- 
bons of  this  empirical  formula  by  condensing  isoprene  with  various 

nJ.  Chem.  Boo.  10S,  1242   (1918). 


THE  CYCLOHEXANE  SERIES  311 

terpenes  by  heating  them  together  in  sealed  tubes.  Very  little  is 
known  regarding  the  constitutions  of  the  sesquiterpenes  beyond  the 
fact  that  some  are  acyclic  and  have  four  double  bonds,  some  are 
monocyclic  and  have  three  double  bonds,  some  are  bicyclic  having 
two  double  bonds  and  others  are  tricyclic  and  have  only  one  double 
bond.  It  will  readily  be  understood  that  the  possible  number  of 
isomeric  hydrocarbons  is  very  great  and  it  now  appears  that  most  of 
the  hydrocarbons,  described  in  the  literature  of  twenty  years  ago  as 
definite  hydrocarbons,  are  in  reality  mixtures  and  that  the  separation 
of  pure  individual  hydrocarbons  from  such  mixtures  is  a  difficult  task 
indeed.  Also  it  was  usually  assumed  in  the  literature  that  the  hydro- 
carbons regenerated  from  crystalline  derivatives,  such  as  the  dihydro- 
chlorides,  were  identical  with  the  original  hydrocarbons,  whereas  many 
instances  are  known  in  which  the  structure  of  the  regenerated  hydro- 
carbon is  quite  different  from  the  original. 

The  monocyclic  sesquiterpenes  are  probably  derivatives  of  cyclo- 
hexane  and  are  accordingly  so  classified.  The  physical  data  are  often 
very  helpful  in  showing  whether  the  sesquiterpenes  are  monocyclic, 
bicyclic  or  tricyclic.  As  noted  by  Parry  88  the  following  constants  are 
typical  of  these  several  groups. 

M  ol.  Refraction 
Specific  Gravity  (Calculated) 

Monocyclic  sesquiterpenes   0.875  to  0.890  67.76 

Bicyclic  "  0.900  "   0.920  66.15 

Tricyclic  0.930  "   0.940  64.45 

Catalytic  hydrogenation  by  Paal's,  Skita's  or  Willstatter's  methods 
and  the  reactions  with  hydrogen  chloride  or  hydrogen  bromide  also 
indicate  the  number  of  double  bonds  in  the  hydrocarbon,  hydrogena- 
tion being  more  certain  since  conjugated  linkings  frequently  do  not 
add  the  maximum  number  of  molecules  of  halogen  acid. 

Zingiberene  and  Zingiberol:  This  sesquiterpene  occurs  in  ginger 
oil.  According  to  Semmler  and  Becker89  it  is  monocyclic  and  con- 
tains three  double  bonds,  one  of  which  is  in  the  ring  and  two  in  the 
side  chain.  The  molecular  refraction  indicates  that  two  of  these 
double  bonds  are  in  conjugated  positions;  MR  =  68.37,  calculated  for 
Ci5H24/-3  is  67.86.  This  optical  evidence  is  also  supported  by  its 
chemical  behavior,  forming  a  dihydrochloride,  melting  at  169°-170°. 
Catalytic  hydrogenation  in  the  presence  of  platinum  gives  hexahydro- 

«  "The  Chemistry  of  Essential  Oils,"  Ed.  Ill,  Vol.  I,  71. 
*>Ber.  tft  1914   (1913). 


312       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

zingiberene  C15H30,  but  reduction  by  sodium  and  alcohol  yields  the 
monocyclic  dihydrozingiberene,  C15H26,  which  also  is  good  evidence  of 
the  existence  of  two  conjugated  double  bonds,  and  since  this  reduction 
takes  place  very  readily  Semmler  concludes  that  these  conjugated 
double  bonds  are  in  the  side  chain.  As  with  other  substances  contain- 
ing conjugated  double  bonds,  zingiberene  resinifies  and  polymerizes 
very  readily  on  standing  in  the  air  or  warming  with  sodium.  Semmler 
and  Becker  state  that  when  zingiberene  is  treated  in  acetic  acid  solu- 
tion with  a  little  sulfuric  acid,  that  it  is  condensed  to  a  bicyclic  isomer 
which  they  have  named  isozingiberene.  They  have  proposed  the  fol- 
lowing constitution  for  these  two  hydrocarbons 


,— CH, 


X. 


:-CH, 


CH^N 


Zingiberene 


-3  ^ 

Isozingiberene 


Zingiberene  forms  a  nitrosochloride  melting  at  96°-97°  and  a  nitrosite 
melting  at  97°-98°(  by  treating  zingiberene  in  cold  petroleum  ether 
with  acetic  acid  and  sodium  nitrite).  A  nitrosate  melting  at  86° 
(with  decomposition)  is  formed  by  treating  the  hydrocarbon,  dis- 
solved in  cold  glacial  acetic  acid,  with  ethyl  nitrite  and  slowly  adding 
nitric  acid. 

Zingiberene  is  associated  in  the  essential  oil  of  ginger,  with  a 
sesquiterpene  alcohol,  zingiberol,90  which  yields  zingiberene  on  decom- 
position by  warming  gently  with  potassium  acid  sulfate.  The  alcohol 
is  partially  decomposed  on  treating  with  acetic  anhydride  and  does 
not  readily  yield  a  phenylurethane,  and  on  treating  the  alcohol  with 
hydrogen  chloride  or  hydrogen  bromide  in  acetic  acid,  the  dihydro- 
chloride  and  dihydrobromide  respectively,  of  zingiberene  are  formed. 
The  alcohol  is  evidently  a  tertiary  alcohol  and  from  its  relations  to 
zingiberene  the  hydroxyl  group  must  be  situated  at  positions  (8)  or 

80  Brooks,  J.  Am.  Chem.  Soc.  38,  430   (1916). 


THE  CYCLOHEXANE  SERIES  313 

(12)  in  the  above  figures.     The  alcohol  has  a  persistent  -aroma  of 
ginger  oil  but  does  not  have  the  sharp  taste  of  the  "gingerol"  discov- 
ered by  Garnett  and  Greier91  and  recently  shown  by  Nelson,92  and 
others  93  to  be  a  phenol  derivative.     [Cf.  particularly  Lapworth,  Pear- 
son and  Royle.]    Zingiberol  distills  at  154°-157°  (14.5  mm.). 

The  physical  properties  of  zingiberene,  and  isozingiberene  e^  as 
follows, 

Zingiberene  Iso-zingiberene 

BoUing-point    .  128°-129°  (9  mm.)  118°-122°(7mm.) 

d  0.8684  0.9118 

20° 
n       ..............................  1.4956  1.5062 

D 
Mol.  Ref.  calc.  for  CaH*/^  ......  67.86 

"     found  68.37  66.50 

"        "     calc.  for  CuH*/^  ......  66.15 


According  to  Semmler  and  Becker  the  dihydrochloride  noted  above 
is  really  a  derivative  of  isozingiberene  since  the  latter  hydrocarbon  is 
formed  from  the  dihydrochloride  by  digesting  with  alcoholic  caustic 
potash.  Hydrogenation  by  platinum  black  in  acetic  acid  yields  hexa- 
hydrozingiberene,  C15H30,  boiling-point  128°-129°  (11  mm.)  d20° 

0.8264,  nj)  1.4560.    Isozingiberene  adds  only  four  atoms  of  hydrogen 

to  form  the  saturated  bicyclic  hydrocarbon.  Like  myrcene  and  other 
conjugated  dienes,  zingiberene  is  readily  condensed  by  heating  at  about 
215°  to  a  bicyclic  isomer,  and  to  a  dimeride,  C30H48,  boiling-point 
260°-280°  (11  mm.),  d20o  0.9287. 

A  synthetic  monocyclic  sesquiterpene  has  been  made  by  Roenisch  94 
in  a  manner  which  leaves  little  doubt  as  to  its  constitution  and  may 
properly  be  named  isoamyl-<x-dehydrophellandrene.  By  treating  car- 
vone  with  isoamyl-magnesium  iodide  (in  benzene  solution)  he  obtained 
the  unsaturated  hydrocarbon,  boiling-point  130°-132°  (11  mm.) 
d22o  0.8679,  [a]D  +  18°  30',  nD  1.49478. 

"Chem.  Zentr.  1907,  II,  924;  1909,  II,  1593. 
92  J.  Am.  Ghem.  Soc.  41,  1115   (1919)  ;  42,  597  (1920). 

"Nomura,  Chem.  Aba.  1917,  2662;  Lapworth,  Pearson  and  Royle,  J.  Ghem.  Soc.  Ill, 
777  (1917). 

M  Schimmel  &  Co.,  Semi-Ann.  Rep.  1917,  20. 


314      CHEMISTRY  OF  THE  NON-BENZEN01D  HYDROCARBONS 
CH3  CH3 


F=0 


CH2 
CH(CH1 


1 CH-CH, 

CH 
CH^  ^ 


CKT 


The  synthetic  hydrocarbon  does  not  give  a  solid  hydrochloride  but  is 
readily  hydrogenated  by  Willstatter's  method  to  the  hydrocarbon 

Bisabolene,  C15H24:  This  sesquiterpene  is  monocyclic,  contains 
three  double  bonds  and  yields  a  trihydrochloride  C15H27C13,  melting  at 
79°-80°.  Its  constitution  is  not  known  but  it  is  probably  a  derivative 
of  cyclohexane.  It  was  originally  discovered  in  the  essential  oil  of 
Bisabol  myrrh  but  has  since  been  found  in  other  essential  oils,  a  speci- 
men isolated  from  lemon  oil  by  Gildemeister  and  Miiller  95  having  the 
following  physical  properties,  boiling-point  110°-112°  (4  mm.),  d-j^o 

0.8813,  [a]D— 41°  31',  nD  1.49015.     The  regenerated  hydrocarbons, 

ebtained  by  heating  the  trihydrochloride  with  sodium  acetate,  distilled 
at  261°-262°.  Bisabolene  does  not  form  a  crystalline  nitrosochloride, 
nitrosite  or  nitrosate. 

"Schimuiel  &  Co..  Semi-Ann.  Rep.  1909  (2),  50. 


Chapter  IX.     Cyclic  Non-benzenoid 
Hydrocarbons: 

The  Para-menthane  Series. 
(1)  Limonene  and  Dipentene. 

Limonene  occurs  in  a  very  large  number  of  essential  oils.  Dextro- 
limonene  is  found  as  the  major  constituent  in  the  citrus  oils,  sweet 
orange  peel,  lemon,  bergamot,  lime,  mandarin  orange  and  petit-grain 
oil,  also  the  essential  oils  of  ginger  grass,  camphor,  Manila  elemi, 
caraway  and  other  oils.  It  is  most  conveniently  isolated  from  oil 
of  sweet  orange  peel,  constituting  about  90  per  cent  of  this  oil.  Lcevo- 
limonene  is  found  chiefly  in  the  leaf  oil  of  the  silver  fir,  turpentine 
from  Pinus  serotina  of  the  southern  United  States,  one  of  the  species 
of  eucalyptus,  Eucalyptus  staigeriana,  American  oil  of  peppermint, 
oil  of  verbena,  American  penny-royal,  etc.  The  optically  inactive 
form,  dipentene,  is  also  found  in  nature  in  the  essential  oils  of  lemon 
grass,  palma-rosa,  ginger  grass,  Siberian  pine  needle,  pepper,  cubeb, 
camphor  oil,  ajowan,  coriander,  nutmeg,  fennel,  cardamom,  etc.  It  is 
also  formed  by  the  racemization  of  d.  or  I.  limonene  by  prolonged 
heating,  by  the  rearrangement  of  less  stable  terpenes  such  as  pinene  * 
and  phellandrene,  by  the  condensation  of  two  molecules  of  isoprene 
and  is  accordingly  found  in  turpentines  made  by  distilling  pine  stumps 
and  the  lighter  fractions  of  rosin  or  copal  oils  made  by  the  destructive 
distillation  of  rosin  or  Manila  copal  and  the  destructive  distillation 
of  caoutchouc.  Formerly  a  number  of  different  names  were  given  to 
this  hydrocarbon,  but  Wallach2  showed  that  the  hydrocarbon  frac- 
tions boiling  at  175°-176°  from  orange  peel  oil  ("hesperidene") ,  lemon 
("citrene"),  caraway  ("carvene") ,  bergamot,  dill  and  pine  needle  oils 
yielded  a  tetrabromide  melting  at  104°,  and  that  the  corresponding 
hydrocarbon  variously  designated  as  cinene,  cajeputene,  kautschin, 

1  On  heating  pinene  with  anhydrous  oxalic  acid  a  mixture  of  dipentene  and  borneol 
esters  are  formed,  cf.  "synthetic  camphor." 
'Ann.  &7f  277   (1885). 

315 


316       CHEMISTRY  OF  THE  NON-BENZENOID-  HYDROCARBC NS 

di-isoprene  and  that  from  camphor  oil,  yielded  a  tetrabromide  melt- 
ing at  125°.  On  isolating  1.  limonene  from  pine  needle  oil  Wallach  3 
showed  that  the  crystalline  tetrabromide  appeared  to  be  identical 
with  the  tetrabromide  from  d-limonene,  except  for  opposite  hemihedral 
crystal  development  (like  Pasteur's  salts  of  tartaric  ac.d),  and  that 
when  equal  portions  of  the  d  and  £-tetrabromides  were  dissolved  and 
crystallized,  the  tetrabromide  melting  at  125°  and  characteristic  of 
dipentene  resulted.  This  relationship  has  since  been  established  for 
other  derivatives  of  limonene  and  dipentene.  It  was  by  such  methods 
that  the  investigation  of  the  terpenes  began  to  be  simplified.  Thus 
the  same  relation  was  shown  to  exist  between  the  nitrolamine  deriva- 
tives of  d  and  Z-limonene  and  those  of  dipentene,  or  the  racemic  forms. 
Wallach  4  discovered  that  when  the  nitrosochlorides  of  d  or  i-limonene 
and  dipentene  were  treated  with  aniline,  condensation  to  the  nitrol- 
anilides  resulted,  there  being  six  forms.  Their  relations  were  made 
clear  by  Wallach  as  indicated  in  the  following  diagram, 
Z-limonene  d-limonene 

a-nitrosochloride  p-nitrosochloride  a-nitrosochloride  p-nitrosochloride 

I  4  j,  | 

a-nitrolanilide        p-nitrolanilide       a-nitrolanlide        p-nitrolanilide 
M.-P.  113°  M.-P.  153°          M.-P.  113°  M.-P.  153° 

\ 

\  \ 

\ 

•  •     \   /\ 

\  ,/        \ 

racemic,  a-dipentene  nitrol-     racemic,  p-dipentene  nitrol- 
anilide,  M.-P.  126°  anilide,  M.-P.  149° 

Physical  Properties:    The  recorded  physical  properties  of  limonene 

20° 
are  the  following:  boiling-point  175°-176°,  d15<>  0.846  to  0.850,  n_ 

1.47459,5    [<x]D=:  +  1250    36',6  — 105°,   --119.410.7    A    sample    of 
dipentene  made  by  destructive  distillation  of  caoutchouc,  examined  by 

•Ann.  2#J,  221    (1888). 

4  Ann.  252.  94   (1889).     For  experimental  details  this  paper  is  recommended. 

8  Wallach,  Ann.  246,  222   (1888). 

"Godlewski  &  Roshanowitsch,  Chem.  zentr.  1899  (1),  1241. 

1  Gildemeister,  "Aetherisohe  Oele,"  Ed.  2,  Vol.  I,  325. 


THE  PARAMENTHANE  SERIES  317 

Schimmel  and  Co.,7  showed  a  boiling-point  of  175°-176°,  d20o  0.844 

20° 
and  n 1.47194.    The  boiling-point  of  dipentene,  177°  to  178°,  is 

usually  stated,  in  the  older  literature,  to  be  higher  than  that  of  limo- 
nene  but  these  higher  boiling-points  (sometimes  given  as  high  as  179°) 
were  probably  due  to  the  presence  of  considerable  high-boiling  ter- 
pinene.  (Until  recently  racemic  compounds  were  believed  not  to 
persist  in  the  liquid  state,  but  Ladenburg 8  has  shown,  in  the  case  of 
pipecoline,  that  this  is  possible,  and  Dunstan  and  Thole 9  have  found, 
by  means  of  viscosity  measurements,  evidence  that  racemic  forms 
may  exist  in  solution.)  Limonene  shows  two  broad  absorption  bands 
in  the  ultraviolet  spectrum,  but  the  absorption  is  increased  in  isomeric 
para  menthadienes  in  which  the  double  bonds  are  nearer  each  other; 
limonene  accordingly  shows  less  absorption  than  other  menthadienes.10 
Perkin  xl  also  showed  that  limonene  has  a  lower  magnetic  rotation, 
M  =  11.24,  than  the  isomer  A3-8<9>  menthadiene,  M  =  13.06,  the 
double  bonds  in  the  latter  hydrocarbon  being  in  the  conjugated  posi- 
tions. 

Limonene  and  dipentene  are  most  conveniently  identified  by  means 
of  their  tetra-bromides,12  which  are  best  prepared  by  adding  the  cal- 
culated amount  of  bromine  to  the  hydrocarbon  dissolved  in  about  four 
volumes  of  acetic  acid,  keeping  the  mixture  chilled  during  the  gradual 
addition  of  the  bromine.  Remarkably  high  yields  of  the  nitroso- 
chlorides  of  limonene  and  pinene  can  be  obtained  by  following  the 
method  recently  described  by  Rupe.13  Concentrated  sulfuric  acid  and 
concentrated  sodium  nitrite  solution  are  separately  dropped  into  a  flask 
containing  a  thin  paste  of  common  salt  and  concentrated  hydrochloric 
acid.  The  evolved  gases  are  cooled,  dried  by  passing  through  calcium 
chloride  and  then  passed  into  a  solution  of  limonene  in  one  volume 
of  ether  and  one  half  volume  of  glacial  acetic  acid,  cooled  in  ice  and 
salt.  Heating  limonene  or  dipentene  nitrosochlorides  with  alcoholic 
caustic  alkali  yields  carvoxime.14  Both  d  and  £-carvoxime  melt  at 
72°  but  the  racemic  carvoxime,  derived  from  dipentene,  melts  at  93°. 
When  limonene  nitrosochloride  reacts  with  sodium  azide  the  chlorine 

8  Bcr.  tf,  2374    (1910). 

•J.   Chem    Soc.  93,  1815    (1908);  .97,  1249    (1910).     Evidence  of  racemic  menthyl 
mandelates,  cf.  Findlay,  J.  Chem.  Soc.  91,  905   (1907). 
10Hantzsch,  Ber.  45,  553    (1912). 
11  J.  Chem.  Soc.  89,  854   (1906). 
"Power  &  Kleber,  Arch.  Pharm.  232,  646   (1894). 
13  Helv.  chim.  Acta.  4,  149  (1921). 
"Deussen  &  Hahn,  Chem.  Zentr.  1910  (1),  1142. 


318       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

atom  is  replaced  by  the  azide  group  N3 ;  the  resulting  nitroso-azide  also 
yields  carvoxime  on  decomposition.15 

Oxidation  of  limonene  in  the  presence  of  water  yields  carvone, 
carveol  (q.v.)  and  a  resin.16  Oxidation  of  limonene  by  chromyl 
chloride  yields  chiefly  cymene  which  is  then  further  oxidized  to 
a-p-tolylpropaldehyde  and  p-tolylmethyl  ketone,17  resembling  terpi- 
nene  in  this  respect,  but  in  the  case  of  limonene  much  more  resin  is 
formed.  Condensation  of  limonene  with  formaldehyde  brought  about 
by  the  use  of  para-formaldehyde  in  glacial  acetic  acid  with  the  addi- 
tion of  a  little  sulfuric  acid,  yields  an  unsaturated  alcohol  homo- 

19° 

limonenol,  boiling-point  122°-126°  at  13  mm.,  d—  0.9720.  Accord- 
ing to  Prins 18  addition  of  formaldehyde  to  a  double  bond  occurs  to 
give  an  oxide  ring  which  may  then  hydrolyze  to  a  glycol,  which  in 
turn  decomposes  to  give  an  unsaturated  alcohol,  as  in  the  case  of 
limonene,  or  many  yield  a  methylene  ether,  as  indicated  in  the  fol- 
lowing, 

R 
RCH  =  CHR >  RCH  — CHR >  RCH  — CH< 

H,i-  -4 


CH2OH 


RC  =  CHR  R 

RCH  — CH< 
H,OH  or 


0 
CH2  — 0 CH2 

This  reaction  with  formaldehyde  has  also  been  studied  by  Prins  in  the 
cases  of  pinene,  camphene,  cedrene,  etc.  When  dipentene  dihydro- 
chloride,  a  by-product  in  the  manufacture  of  artificial  camphor,  is 
treated  with  chlorine  to  form  a  trichloromenthane  and  this  product 
decomposed,  cymene  is  formed.19 

Carvomenthene:  (A1-p-menthene?). 

When  limonene  is  hydrogenated  in  the  presence  of  platinum  black, 
the  reduction  proceeds  in  two  stages,  the  first  product  being  carvo- 
menthene  and  the  final  product  paramenthane.20  Carvomenthene 

"Forster  &  Gelderen,  J.  Chem.  Soc.  99,  2061   (1911). 

"Blumann  &  Zeitschel,  Ber.  p,  2623   (1914). 

"Henderson  &  Cameron,  J.  Chem.  Soc.  95,  972   (1909). 

uChem.  Abs.  H,  1662    (1920). 

"Brit.  Pat.  142,738   (1919). 

"Vavon,  Butt.  Soc.  chim.   (4)  15,  282   (1914). 


THE  PARAMENTHANE  SERIES  319 

made  in  this  manner  is  optically  active,   [a^yg   +118°.  .Bacon21 

prepared  carvomenthene  from  limonene  monohydrochloride  (by  HC1 
in  cold  carbon  bisulfide  solution)  by  making  the  Grignard  complex, 
magnesium  limonene  hydrochloride,  and  decomposing  this  with  water. 
However,  racemization  accompanies  the  formation  of  the  hydro- 
chloride.  Bacon  also  made  the  hydrochloride  of  carvomenthene  and 
reduced  it  to  para-menthane  in  the  same  manner  by  means  of  the 
Grignard  reaction.  Carvomenthene  boils  at  175°-177°,  its  hydro- 
chloride  boils  at  85°-86°  (13  mm.)  and  the  nitrosochloride  melts 
at  95°. 

Para-menthane:  By  the  catalytic  reduction  of  limonene  by  hydro- 
gen in  the  presence  of  platinum  black,22  by  the  hydrogenation  of  para- 
cymene  in  the  presence  of  catalytic  nickel  23  and  by  heating  the  semi- 
carbazone  or  hydrazone  24  of  menthone  with  sodium  ethylate  at 

15° 

160°-170°,  para-menthane  is  produced,  boiling-point  169°,  d  _  0.803. 

15 

In  the  latter  process  heating  the  semicarbazone  at  160°  first  forms 
the  hydrazone  which  subsequently  decomposes  to  the  hydrocarbon, 


>C  =  N.NH.CONH2  +  H20  ---  >>C  =  N.NH2  +  C02  +  NH3 

The  Constitution  of  Limonene:  The  structure  of  limonene  is  inti- 
mately related  to  the  structure  of  terpineol,  terpin  and  carvone. 
Til.den  25  and  Wallach  26  had,  at  an  early  date,  shown  that  when  terpin 
is  digested  with  dilute  acids,  it  yields  terpineol  and  that  by  more 
energetic  dehydration  terpineol  also  decomposes  further,  forming 
water  and  dipentene. 

C10H18(OH)2  -     ->  C10H17.OH  -      -*  C10H16 
terpin  terpineol  dipentene. 

Terpineol  and  terpin  are  converted  by  hydrogen  chloride  to  a  crystal- 
line dichloride  27  C10H18C12  melting  at  50°,  which  is  identical  with  the 
dihydrochloride  made  from  dipentene.26  The  position  of  the  double 
bond  in  terpineol  was  suggested  by  Wallach  28  and  confirmed  by  later 
researches  of  Baeyer  29  and  others,  particularly  on  the  ground  of  the 

21  Philippine  J.  Sci.  1908,  52. 

22Vavon,  Compt.  rend,  Ufl,  997   (1909). 

23  Sabatier  &  Senderens,  Compt.  rend.  156,  184  (1913). 

2«Wolff,  Ann.  39*,  86   (1912). 

"Bcr.  12,  848   (1879)  ;  J.  Chem.  Soc.  S5,  287   (1879). 

28  Ann.   230,  258    (1885). 

2TList,  Ann.  67,  367   (1848). 

28  Ann.   277,  105    (1893). 

"Ber.  26,  2558   (1893). 


320      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

relations  between  terpineol  and  carvone  (see  below).    Wallach's  pro- 
posed constitution  of  terpineol  was 

CH, 


This  proposed  structure  was  open  to  the  objection  that  such  a  sub- 
stance could  not  decompose  with  loss  of  water  to  give  a  hydrocarbon 
containing  an  asymmetric  carbon  atom,  whereas  Wallach  himself 
had  shown  that  dipentene  was  a  mixture  of  the  two  active  d  and 
Mimonenes.  A  little  later,  1894,  Wagner 30  published  his  well-known 
paper  "On  the  oxidation  of  cyclic  compounds,"  in  which  he  modified 
Wallach's  terpineol  structure  to 


H 


C— OH 


which  is  abundantly  supported  by  other  evidence  published  since,  of 
which  probably  the  most  convincing  is  W.  H.  Perkin,  Jr.'s  synthesis 
of  terpin,  terpineol  and  a  series  of  related  substances.81 

*«Ber.  27,  1636   (1894). 

81  8th  Int.  Cong.  Appl.  Ctiem.  VI,  224  (1912). 


THE  PARAMENTHANE  SERIES  321 

CH3 
The  group    R  —  C  —  OH     is  readily  synthesized  by  the  action 

CH3 

of  zinc  methyl,  and  particularly  easily  by  the  action  of  magnesium 
methyl  iodide  on  acid  chlorides,  esters  or  methyl  ketones  and  Perkin 
accordingly  carried  out  his  synthesis  as  follows: 

(1)  Pentane-1,  3,  5-tricarboxylic  acid  was  heated  with  acetic  anhy- 
dride when  C02  and  water  were  eliminated  and  cyclohexanone-4-car- 
boxylic  acid  was  formed. 

H02C.CH2CH2  CH2CH2 

>CH.C02H >  OC<  >CH.C02H 

H02C.CH2CH2  CH2CH2 

(2)  The  ester  of  this  acid  was  then  treated  with  methyl-magnesium 
iodide  in  the  usual  manner  when  the  ketone  group  reacts  much  more 
readily  than  the  C02R  group ;  the  resulting  hydroxy  acid  was  converted 
to  the  corresponding  bromide  by  heating  with  hydrobromic  acid  and 
the  resulting  tertiary  bromide  digested  with  sodium  carbonate,  remov- 
ing HBr  to  give  l-methyl-A1-cyclohexene-4-carboxylic  acid. 

CH2CH2  HO  CH2CH2 

OC<  >CH.C02R >          >C<  >CH.C02R 

CH2CH2  CH3          CH2CH2 

Br  CH2CH2\  /CH.CH2 

->        >C<  CH.C02H-»CH3  — C  >CH.C02H 

CH3          CH2CH2/  \CH2CH2 

1 

(3)  On  treating  the  ester  of  this  acid  with  methyl-magnesium 
iodide  an  almost  quantitative  yield  of  a-terpineol  was  obtained. 

CHCH2  CHCH2  CH3 

CH3C  '  CH.C02R  -*  CH3C  CH  —  C  —  OH 

CH2CH2  CH2CH2  CH3 

a-Terpineol  is  characterized  by  its  fine  odor  of  lilacs  and  is  manu- 
factured in  comparatively  large  quantities  by  decomposing  terpin 
hydrate  or  terpin  (made  from  pinene)  by  means  of  phosphoric  acid. 
Unless  specially  purified  the  commercial  product  is  liquid  at  ordinary 
temperatures  and  contains  a  little  p-terpineol 82  melting  when  pure  at 

"Stephan  &  Helle,  Ber.  55,  2147   (1902). 


322      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

32°,  and  the  liquid  terpinenol-1.33  In  nature,  only  a-terpineol  ap- 
pears to  be  formed.  Terpineol  is  the  major  constituent  of  commercial 
long  leaf  pine  oil 34  made  by  distilling  the  wood  with  steam.  A  good 
commercial  pine  oil  will  show  75  per  cent  distilling  between  211°  and 
218°.  It  has  proven  particularly  valuable  for  the  concentration  of 
low-grade  copper  ores  by  the  flotation  process.  The  stability  of  ter- 
pineol  in  the  presence  of  alkali  renders  it  valuable  in  the  perfuming 
of  soaps.  Commercial  a-terpineol  melts  at  35°,  boils  at  217°-218°  at 
760  mm.,  at  104°-105°  and  10  mm.,  has  a  density  of  0.935  to  0.940  at 

20° 

15°  and  a  refractive  index  n  — 1.4808.35  An  exceptionally  pure  speci- 
men of  a-terpineol,  made  by  Wallach  36  by  the  action  of  dilute  sulfuric 
acid  on  homonopinol,  showed  melting-point  37°-38°,  boiling-point 
218°-219°,  and  fa]D— 106°  (in  16.34  per  cent  solution  in  ether). 

The  highest  optical  activity  observed  for  natural  terpineol  is 
[a]  D+  95°  9'  (from  bitter  orange  peel  oil)  and  [a]D  — 27°  20'  shown 

by  a  specimen  of  Z-terpineol  from  linaloe  oil.  A  specimen  of  synthetic 
/-terpineol37  showed  [a]Q  — 117.5°.  Commercial  terpineol  is  soluble 

in  9  volumes  of  50  per  cent,  in  3  volumes  of  60  per  cent  and  in  about 
2  volumes  of  70  per  cent  alcohol.  When  free  from  water  it  is  miscible 
in  petroleum  ether.  The  nitrosochloride  of  d  or  Z-terpineol  melts  at 
107°-108°,  that  of  i-terpineol  at  112°-113°;  the  corresponding  nitrol- 
piperidine  compounds  melt  at  151°-152°  and  159°-160°  respectively. 
By  shaking  terpineol  with  an  excess  of  concentrated  hydriodic  acid 
the  dihydroiodide  C10H18I2  is  formed,  melting  at  77°-78°.  Terpineol, 
being  a  tertiary  alcohol,  is  very  easily  decomposed  with  loss  of  water 
when  heated  with  potassium  acid  sulfate  or  oxalic  acid;  even  acetic 
anhydride  partially  decomposes  it,  on  heating,  forming  dipentene. 
Phenylisocyanate  yields  a  phenylurethane,38  the  inactive  form  melting 
at  113°.  The  a-naphthylurethane 39  melts  at  147°-148°.  As  with 
most  tertiary  alcohols,  the  phenyl  and  naphthylurethanes  are  difficult 
to  prepare,  partial  decomposition  of  the  alcohol,  with  the  formation 
of  water,  causing  the  conversion  of  phenyl  isocyanate  to  diphenyl  urea. 
In  preparing  the  isocyanate  it  is  advisable  to  separate  the  crystals  of 

83  Wallach,  Ann.  362,  269    (1908). 

"Teeple,  J.  Am.  Chem.  Soc.  30,  412   (1908)  ;  Met.  &  Chem.  Eng.  11,  247   (1913). 

"8  Gildemeister,  "Aetheriache  Oele,"  Ed.  2,  Vol.   I,  394. 

*«Ann.  360,  89   (1908). 

87  Ertschikowsky,  Bull.  aoc.  chim.    (3)    16,  1584    (1896). 

88  Wallach,  Ann.  275,  104   (1893). 
"Schimmel  &  Co.   Semi-Ann.  Rep.  1906   (2),  33. 


THE  PARAMENTHANE  SERIES  323 

diphenyl  urea,  which  first  form,  by  taking  up  the  liquid  portion  in  a 
little  perfectly  dry  ether.  The  mixture  should  be  permitted  to  stand 
three  or  four  days  protected  from  the  moisture  of  the  air.  Good 
yields  of  terpinyl  hydrogen  phthalate  and  succinate  can  be  obtained 
by  allowing  an  excess  of  the  alcohol  to  stand  with  the  acid  anhydride 
at  temperatures  below  1000.40  The  d-glucosides  of  both  a  and  p-terpi- 
neol  have  been  made  by  treating  |3-tetra-acetylbromoglucose  in  ethyl 
ether  with  an  excess  of  the  terpene  alcohol  in  the  presence  of  silver 
carbonate.  The  acetyl  groups  are  removed  from  the  product  by  means 
of  barium  hydroxide.  The  resulting  glucosides  are  rapidly  hydrolyzed 
by  hot  dilute  acids  but  are  very  slowly  split  by  emulsin.41  Glucosides 
of  citronellol  and  of  dihydrocarveol  were  prepared  in  the  same  manner. 
It  is  practically  certain  that  glucosides  of  many  terpene  alcohols  exist 
in  nature,  in  addition  to  the  few,  such  as  coniferin,  which  are  known 
to  occur  in  nature. 

Tertiary  alcohols  appear  to  be  capable  of  forming  addition  products 
with  chromic  acid,  when  the  alcohols  are  dissolved  in  an  inert  solvent 
and  shaken  with  concentrated  chromic  acid  or  the  solid  crystals.  In 
the  case  of  a  and  p-terpineols  the  addition  products  are  liquid  and 
unstable.42 

The  hydration  of  a-terpineol  to  terpin  hydrate  can  be  beautifully 
demonstrated,  as  for  a  lecture  experiment,  by  dissolving  terpineol  in 
5  parts  of  80  per  cent  phosphoric  acid  at  30°,  allowing  to  stand  a  few 
minutes  and  then  diluting  about  six  times  with  cold  water,  when  within 
a  few  minutes  a  bulky  matted  mass  of  crystals  of  terpin  hydrate  will 
form.43  The  reaction  is  less  complete  with  60  per  cent  sulfuric  acid 
and  Aschan  44  has  shown  that  45  per  cent  sulfuric  acid,  shaken  with 
pinene  for  16  hours  at  +  1°  gives  a  yield  of  53  per  cent  terpin.  The 
ease  of  making  terpin  hydrate  from  commercial  long  leaf  pine  oil  has 
been  pointed  out  by  Teeple.45 

The  synthetic  a-terpineol  made  by  Perkin  was  converted  into  terpin 
hydrate  by  agitating  with  dilute  sulfuric  acid;  by  heating  with  potas- 
sium hydrogen  sulfate  dipentene  was  obtained,  thus  completing  the 
synthesis  of  these  three  important  substances.  Additional  proof  of  the 
constitution  of  terpin  was  furnished  by  Perkin  and  Kay,  who  showed 

"Pickard,  Lewcock  &  Yates,  Proc.  chem.  8oc.  29,  127    (1914) 
41  Haemaelaeinen,  Biochem.  Z.  49,  398    (1913)  '' 

42Wienhaus,  Ber.  47,  322   (1914). 

43  Prins,  Chem.  Abs.  1917,  2773. 

44  Chem.  Aba.  1919.  2759. 
45Loc.  cit. 


324       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

that  when  ethyl  cyclohexanone-4-carboxylate  was  treated  with  large 
excess  of  methyl-magnesium  iodide,  terpin  is  formed. 


l.S-terpin. 

This  synthesis  proves  conclusively  the  position  of  the  two  hydroxyl 
groups  in  terpin. 

Terpin  Hydrate  is  not  known  to  occur' in  essential  oils.  It  melts 
at  116°-117°  and  readily  loses  a  molecule  of  water  on  heating  or  on 
standing  over  sulfuric  acid  to  form  terpin,  melting-point  104°,  whose 
structure  is  shown  above.  Terpin  exists  in  two  stereo-isomeric  forms 
of  the  cis  and  trans  type.46  Terpin  derived  from  terpin  hydrate  by 
dehydration  is  the  cis  form;  the  trans  form,  melting-point  156°-158°, 
is  made  from  frans-dipentene  dihydrobromide  and  silver  acetate, 
jfrans-terpin  does  not  crystallize  with  water  of  crystallization. 

Other  evidence  for  the  structure  of  limonene,  a-terpineol  and  terpin 
had  already  shown  their  constitution  with  reasonable  certainty. 
Wagner  had  proposed  his  now  accepted  constitution  of  a-terpineol 
largely  to  overcome  the  objection  made  against  Wallach's  constitution, 
that  the  latter  could  not  give  an  optically  active  hydrocarbon,  limo- 
nine,  on  dehydration.  By  oxidizing  a-terpineol  first  with  perman- 
ganate and  then  with  chromic  acid,  Wallach  47  obtained  a  series  of 
oxidation  products  finally  resulting  in  homoterpenylic  and  terpenylic 

"Baeyer,  Ber.  26,  2865  (1893)  ;  29,  5  (1896).  Van't  Hoff,  in  1874,  had  predicted 
that  cyclic  compounds  of  this  type  would  be  found  to  exist  in  two  stereo  isomeric 
forms. 

227,  110   (1893). 


THE  PARAMENTHANE  SERIES 


325 


acid  and  he  showed  that  these  changes  could  readily  be  interpreted  by 
Wagner's  constitution  for  a-terpineol,  i.e., 


H, 


'-OH 
^CH, 

a-terpineol 


VMV\r\CL 


Homoterpenylic  acid        Terpenylic  acid 


Although  the  constitution  of  these  important  acids  was  worked  out 
with  reasonable  certainty  48  their  synthesis  by  Lawrence  and  Simon- 
sen  *9  removes  all  question  as  to  their  structure.  The  constitution  of 
these  acids  also  has  a  very  direct  bearing  on  the  constitution  of 
pinene  and  Simonsen's  synthesis  is  therefore  mentioned  in  outline  as 
follows, 

«Wallach  (Ann.  259,  322  [1890]),  had  suggested  the  above  constitution  for  ter- 
penylic  acid  and  its  correctness  has  been  confirmed  by  the  work  of  Fittig  (Ann.  t88, 
176  [1896]),  Mahla  and  Tiemann  (Ber.  29,  928  [1896]),  and  Schryver  (J.  Ohem.  Soc. 
63,  1338  [1893]). 

*9  J.  Chtm.  Soc.  75,  527   (1899)  ;  91,  184  (1907). 


326       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


CCLR 


(a) 


\ 


\/ 

CH 

io 

CH, 


C02R 


HC  CH 


CH3MgI 


C02R 
H2C 

CH 

C-OH 
/\ 


C02R 
H2 


CH, 


CH, 


C==0 


CH,     ^CH3 


When  the  latter  ester  is  hydrolyzed  with  hydrochloric  acid,  C02  is 
eliminated;  the  ester  of  the  resulting  p-acetyladipic  acid  yields  homo- 
terpenylic  acid  (ester)  when  treated  with  magnesium-methyl  iodide, 
as  in  (a). 

The  above  work,  together  with  Perkin's  synthesis,  conclusively 
proves  the  position  of  the  double  bond  in  a-terpineol.  The  position  of 
the  other  double  bond  in  limonene  was  shown  by  reference  to  the  con- 
stitution of  carvone  and  dihydrocarveol.  The  nitrosolimonene  of 


THE  PARAMENTHANE  SERIES 


327 


Tilden  and  Shenstone 50  proved  to  be  identical  with  carvoxkne,51  from 
which  it  follows  that  at  least  one  and  perhaps  both  double  bonds  in 
limonene  and  in  carvone  are  similarly  situated.  On  reduction  of 
carvone  one  double  bond  is  saturated  yielding  dihydrocarveol,  which 
on  oxidation  first  by  permanganate,  followed  by  chromic  acid  and 
sodium  hypobromite,  finally  yields  2-hydroxy-para-toluic  acid,  which, 
when  the  intermediate  products  are  also  considered,  indicates  that 
the  double  bond  in  dihydrocarveol  is  in  the  side  chain.52 


Dihydrocarveol 


/H 


CH, 


NaOB 


OH 


2-hydroxy- 

para-toluic 

acid 


The  above  facts  make  clear  the  relations  between  limonene,  a-ter- 
pineol  and  terpin,  and  the  dihydrohalogen  derivatives  obtained  from 
all  three,  i.e., 


80  J.  Chem.  Soc.  SI,  554    (1877). 

81  Goldschmidt  &  Ziirrer,  Ber.  18,  2220   (1885). 

"Wallach,  Ann.  275,  110  (1893)  ;  Tiemann  &  Semmler,  Ber.  28,  2141   (1895). 


328       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

»,  W 


by  ^5  acetate 
and  hydrolysis 


The  Constitution  of  Carvone. 

The  conversion  of  carvone  to  carvacrol,  and  carvoxime  to  carva- 
crylamine  were  early  observed  and,  though  not  understood,  served  to 
call  attention  to  the  probability  that  carvone,  carvoxime  and  limonene 
were  para-menthane  (l-methyl-4-iso  propylcyclohexane)  derivatives 
and  that  the  oxygen  atom  in  carvone  occupied  position  (2) .  Wagner  53 
with  his  usual  perspicacity,  proposed  a  constitution  for  carvone  in 
1894,  which  has  proven  correct.  He  based  his  deductions  upon  the 
results  obtained  by  Best54  and  by  Wallach55  on  oxidizing  carvone, 
although  the  constitutions  of  the  oxidation  products  they  obtained 
were  not  then  definitely  known.  Terpenylic  acid  can  be  obtained 
from  carvone  in  the  following  manner,  the  ring  being  broken  at  two 
points  to  give  acetic  acid  as  one  of  the  oxidation  products. 

CHaCO,H  4- 


o  = 

c 

CO 

2H 

/ 

CH2 

CH 

2 

\ 

/ 

X 

i 

H 

0 


Ber.  «7,  2270  (1894). 


CH8          CH2OH 

"Ber.  *7,  1218  (1894).          » Ber.  27,  1496  (1894). 


THE  PARAMENTHANE  SERIES 


329 


0 


C02H. 
H2  CH2 

C\ 

AH 


(by  replacing  OH  by  Br  and 
reducing) 


CH3  '       CH3 

The  relation  between  carvone  and  limonene  is  very  well  shown 
by  Wallach's 56  conversion  of  terpineol  to  carvone  by  removing  hydro- 
gen chloride  from  terpineol  nitrosochloride  by  means  of  caustic  alkali 
and  then  boiling  the  resulting  oxime  with  acids,  thus  hydrolyzing  the 
oxime  to  the  ketone  and  simultaneously  removing  the  original  hydroxyl 
group. 

:H, 

-Cl  .^ 

>N.OH         <tf  ^I=N< 
+  NOO  I      4.KOH 


«<*«[    « 


dil  acids  . 


CH. 

- 


Other  menthadienes  were  made  synthetically  by  W.  H.  Perkin,  Jr., 
and  his  assistants.  A3-8(9>-p-menthadiene  was  made  in  the  following 
manner.  Fara-toluic  acid  was  reduced  by  sodium  and  alcohol  to 
l-methylcyclohexane-4-carboxylic  acid  which  on  bromination,  fol- 
lowed by  removal  of  HBr  by  sodium  carbonate  or  quinoline  in  the 
usual  manner,  yielded  l-methyl-A3-cyclohexene-4-carboxylic  acid 
the  ester  of  which  yields  A3-p-menthenol  (8)  when  treated  with  mag- 

£77,  120  (1893). 


330       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

nesium  methyl  iodide.    On  digesting  this  menthenol  with  potassium 
acid  sulfate  A8>8(9)-p-menthadiene  is  formed. 

CH3 


h3-p-menthenol(8) 

Like  many  substances  having  two  double  linkings  in  the  conjugated 
position,  this  menthadiene  reacts  with  bromine  to  form  a  dibromide 

CHBr  CH2Br 

in  which  the  double  bond  has  shifted  to  the  >  C  =  C  < 

CH2  CH8 

position.  Also,  as  contrasted  with  limonene,  this  menthadiene  is  capa- 
ble of  combining  with  only  one  molecule  of  HC1  or  HBr,  these  products 
being  liquid.  The  same  behavior  toward  bromine  and  HBr  and  HC1 
is  shown  by  the  ortho  and  me£a-menthadiene  derivatives  containing 
conjugated  double  bonds,  i.e., 

CH5  CH} 


THE  PARAMENTHANE  SERIES 


331 


Another  synthesis  of  A3>8(9)-p-menthadiene  was  developed  by 
Perkin  in  collaboration  with  Wallach.57  In  this  synthesis  1-methyl- 
cyclohexane-4-one  is  condensed,  by  the  Reformatsky  reaction  (zinc 
and  a-bromopropionic  ester) ,  to  the  oxy  acid. 


The  oxy  acid  loses  water,  when  digested  with  acetic  anhydride,  and  the 
resulting  unsaturated  acid  decomposes  further  when  distilled,  losing 
C02.  The  semicyclic  hydrocarbon  was  then  converted  into  its  nitroso- 
chloride  and  this  by  eliminating  hydrogen  chloride  by  alkali  yields 
an  oxime  which  was  hydrolyzed  in  the  usual  manner  to  the  ketone. 


CH3 


H, 


h*-p-menthenol(8) 

The  ease  with  which  this  teriary  alcohol  is  decomposed  with  loss  of 
water  to  form  the  A3<8(9>-p-menthadiene  is  worthy  of  note;  shaking 

"Ann.  374,  198   (1910). 


332       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

with  1  per  cent  sulfuric  acid  at  warm  temperature  effects  this  change. 
The  products  obtained  by  these  methods  are,  of  course,  optically 
inactive  and  therefore,  to  obtain  A3-p-menthenol  (8)  of  high  optical 
activity,  Perkin  selected  natural  pulegone  as  his  original  material. 
As  is  well  known,  pulegone  decomposes  on  heating  with  alkali  to  give 
l-methyl-cyclohexane-3-one,  which  in  this  case  showed  [a]j^  +  8°. 

By  treating  this  ketone  with  sodium  amide  and  carbon  dioxide 
l-methyl-cyclohexane-3-one-4-carboxylic  acid  was  formed  which  was 
dehydrated  yielding  d  l-methyl-A8-cyclohexene-4-carboxylic  kicid  of 
high  optical  activity  [a]j)+  150.1° 


l-methyl-h3-cyclohexene-4- 
-carboxylic  acid,  [a]  -    +  150.1 


The  following  physical  properties  of  As-8<9>-p-inenthadiene  were 
noted  by  Perkin  and  Wallach:  boiling-point  184°-185°,  d  —0.858, 

20° 
n  —  1.4924  from  which  the  molecular  refractivity  is  46.02,  calculated 

for  C10H16/=2  is  45.24  showing  the  exaltation  due  to  the  conjugated 
position  of  the  double  bonds. 


THE  PARAMENTHANE  SERIES  333 

Terpinolene  and  the  Terpinenes. 

The  constitution  of  the  terpinenes  has  been  a  matter  of  consider- 
able controversy  but  researches  of  recent  years,  particularly  the  work 
of  Wallach,  has  solved  the  puzzle  in  a  very  satisfactory  manner.  Til- 
den,  Armstrong  and  others  had  studied  the  action  of  mineral  acids 
on  turpentine  or  pinene,  also  limonene  and  the  alcohols,  terpineol  and 
terpin,  but  the  chief  result  of  their  investigations  was  to  the  effect 
that  a  new  terpene,  C10H16,  was  probably  formed.  It  was  not  defi- 
nitely characterized  either  by  physical  constants  or  chemical  deriva- 
tives, and  it  was  given  a  variety  of  names.  In  1885  Wallach 58  applied 
his  tetrabromide  method,  which  he  had  used  in  the  identification  of 
limonene  and  dipentene,  to  the  high-boiling  fraction  boiling  from 
179°-190°,  obtained  by  the  action  of  alcoholic  sulfuric  acid  on  tur- 
pentine. From  this  fraction  he  prepared  a  new  tetrabromide, 
C10H16Br4  melting  at  116°-117°,  thus  proving  the  existence  of  a  new 
terpene,  which  he  named  "terpinolene."  In  the  mixture  of  hydrocar- 
bons resulting  from  the  action  of  alcoholic  sulfuric  acid  on  terpin 
hydrate,  dipentene,  phellandrene  or  cineol,  he  showed  that  the  fraction 
boiling  from  179°-182°  contained  what  he  termed  "terpinene."  This 
fraction  did  not  give  a  crystalline  tetrabromide.  A  fairly  good  yield 
of  terpinolene  was  also  obtained  by  the  action  of  hot  concentrated 
oxalic  or  formic  acid  on  a-terpineol,  the  terpineol  being  slowly  dropped 
into  the  acid  and  the  terpinolene  removed  by  distilling  with  steam  as 
fast  as  formed,  as  otherwise  the  new  terpene  underwent  further  change. 
Being  influenced  by  the  constitution  for  a-terpineol  which  he  had  pro- 
posed, Wallach 59  suggested  the  following  structure  for  terpinolene, 


'CM, 

Although  von  Baeyer  had  accepted  Wallach's  a-terpineol  formula,  he 
nevertheless  advanced  his  now  generally  accepted  A1>4(8>  structure  for 

"Ann.  tin,  283   (1885)  ;  230,  262  (1885). 

"Ann.  227,  145   (1893).     This  formula  was  later  put  forward  by  Harries,  Ber.  95, 
1169,  as  the  constitution  of  terpinene   (q.v.). 


334       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


terpinolene.  Baeyer 60  considered  that  this  structure  was  indicated  by 
the  formation  of  blue  nitroso  derivatives.  The  position  of  the  second 
double  bond  was  indicated  by  its  relation  to  a-terpineol  and  its  optical 
inactivity.  In  view  of  the  fact  that  other  isomeric  hydrocarbons  are 
also  simultaneously  formed  and  that  radical  changes  in  constitution 
are  known  to  be  brought  about  by  heating  with  acids,  these  considera- 
tions would  have  little  weight  were  it  not  for  other  evidence.  Baeyer 
made  terpinolene  by  brominating  limonene  dihydrobromide  and  treat- 
ing the  resulting  tribromide  with  zinc  dust;  saponification  of  the 
resulting  mono-acetate  yielded  a  new  terpineol,  y-terpineol,  melting- 
point  69°-70°.  Baeyer  had  shown  that  other  substances  containing 
the  group  >C  =  C(CH3)2,  for  example,  tetramethylethylene,  give  blue 
nitroso  compounds.  He  had  also  shown  that  generally  dibromides  in 
which  the  two  bromine  atoms  are  in  the  1.2  position  are  reduced  by 
zinc  dust  and  acetic  acid  to  the  olefine  group. 


Br 


"Ber.  «7,  436   (1894), 


CH,   XH, 

y-terpineol 
M.-P.  69°-70° 


CH,   XCH, 
terpinolene 


THE  PARAMENTHANE  SERIES  335 

Also  since  the  nitrosochloride  of  y-terpineol  was  also  blue,  Baeyer 
reasoned  that  this  terpineol  contained  the  >C  =  C(CH3)2  group  as  in 
terpinolene.  Dehydrating  agents  were  shown  to  convert  y-terpineol 
to  terpinolene. 

Semmler61  has  made  a  terpinolene  of  unusual  purity  by  reducing 
terpinolene  tetrabromide  (which  can  be  isolated  from  impure  material) 
by  treating  with  zinc  dust  in  alcohol  instead  of  acetic  acid.  Semmler's 
terpinolene  had  the  following  physical  properties:  Sp.  Gr.  20°,  0.854, 

20° 
n  ^-1.484,  boiling  point  at  10mm.  67°-68°,  boiling-point  at  760mm. 

183°-185°,  optically  inactive.  Heat  converts  terpinolene  to  dipentene 
and  acids  partially  convert  it  to  a  mixture  containing  a  and  yterpi- 
nenes,  dipentene  and  terpinolene.  Terpinolene  is  apparently  not  found 
in  nature;  Clover62  reported  it  in  Manila  elemi,  but  Bacon,63  working 
on  material  from  the  same  source,  was  unable  to  confirm  this.  Terpi- 
nolene is  obtained  as  a  by-product  in  the  manufacture  of  commercial 
terpineol  and  is  occasionally  found  as  an  adulterant  of  lavender  and 
other  oils.  Terpinolene  has  been  synthesized  from  nopinone  and 
methyl  nopinol  (q.v.).64 

The  Terpinenes. 

The  formation  of  "terpinene"  by  the  action  of  alcoholic  sulfuric 
acid  on  pinene,  terpin  hydrate,  cineol,  dipentene  and  phellandrene  has 
been  mentioned  in  connection  with  terpinolene,  which  is  also  formed 
in  the  reaction  mixture.  Its  occurrence  in  nature  was  first  noted  in 
the  case  of  oil  of  cardamoms  by  Weber.65  It  has  been  reported  to 
occur  in  Manila  elemi,  but  according  to  the  researches  of  Clover  and 
Bacon,66  on  over  a  hundred  specimens  of  authentic  material,  different 
individual  trees  yield  an  oleoresin  containing  either  limonene  or  phel- 
landrene of  remarkable  purity ;  the  commercial  oil  accordingly  contains 
both  of  these  terpenes,  but  since  Clover  and  Bacon  worked  with  fresh 
material  it  is  probable  that  the  terpinene  reported  by  others  was 
formed  from  phellandrene  by  the  action  of  formic  or  other  acids 
developed  by  air  oxidation.  "Terpinene"  has  usually  been  identified 
by  means  of  the  nitrosite  melting  at  155°.  According  to  Schimmel 

« Ber.  42,  4644    (1909). 
93  Philippine  J.  Sci.  1907,  1. 
•»  Philippine  J.  Sci.  A.  1909,  93. 
"Wallach.  Ann.  856.  244   (1907). 
**Ann.  238,  107    (1887). 
«•  Philippine  J.  Soi.  1909,  93. 


336       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

&  Co.,6T  Wallach's  a-terpinene  occurs  in  coriander  oil  and  y-terpinene 
in  ajowan,  lemon  and  coriander  oil. 

Terpinene  was  frequently  confounded  with  dipentene,  in  the  earlier 
literature.  Both  yield  crystalline  addition  products  with  halogen 
acids,  but  although  the  melting  points  of  the  corresponding  dihydro- 
halides  are  very  close  together,  a  marked  lowering  of  the  melting- 
point  results  when  the  two  are  mixed.  The  terpinene  dihydrohalides 
are  best  prepared  from  sabinene. 

"Terpinene"  Dipentene 

C1«HM.2HC1  51°-52°  50° 

CioHw.2HBr   58°-59°  64° 

CioHw.2HI   76°  77° 

Wallach  68  has  shown  that  with  aqueous  alkali  the  dihydrochloride  is 
converted  into  a  terpin  melting  at  137°  and  not  identical  with  cis  or 
trans-  1.8-terpin  which  corresponds  to  limonene  dihydrochloride. 
Wallach  reasoned  that  if  the  new  terpin  was  a  di-tertiary  alcohol,  as 
its  behavior  indicated,  it  must  have  the  structure  of  1 . 4-dihydroxy- 
p-menthane,  if  it  was  in  fact  a  para-menthane  derivative.  It  was 
further  distinguished  from  ordinary  or  1.8-terpin  by  the  formation 
of  an  oxide  differing  from  cineol  (eucalyptol).  It  should  be  men- 

:a 


l.8-Terp 


in 


M.-P.  cis-  102°-105°     —  H2O 
trans-  156°-158° 


1.8  cineol 


L-t-terpm 


)H 


M.-P.  cis-  116°-117° 
trans-  137° 


—  H20 


1.4  cineol 


«  Gildemeister  &  Mtiller,  Wallach-Festschrift  1909,  443. 
••Ann.  350,  157   (1906)  ;  356,  200   (1907). 


THE  PARAMENTHANE  SERIES 


337 


tioned  that  on  dehydrating  ordinary  terpin,  one  of  the  products  is  the 
oxide,  cineol,  which  has  been  shown  to  be  an  oxygen  ether,  or  oxide, 
the  oxygen  atom  of  which  is  attached  to  the  carbon  atoms  1  and  8. 
The  difference  between  the  two  terpins  and  their  oxides  are,  as  sug- 
gested by  Wallach. 

Additional  evidence  that  this  is  the  constitution  of  the  new  terpin 
was  furnished  by  its  synthesis 69  from  sabina  ketone.  (Sabinene  and 
sabina  ketone,  q.v.,  had  already  been  shown  to  contain  an  unstable 
tri-carbon  ring,  as  shown.) 

CH3  CH3 

-OH  JL-OH 


Reduction  of  ascaridol  (q.v.)  also  yields  1.4-terpin. 

It  will  be  evident  that  1.4-terpin,  or  the  corresponding  dihydro- 
chloride,  can  conceivably  decompose  with  loss  of  two  molecules  of 
water  or  hydrochloric  acid,  respectively,  to  give  four  different  para- 
menthadienes,  i.e., 


H3 


XH3 

a-terpinene       $-terpinene  y-terpinene         terpinolene 

Of  the  hydrocarbons  represented  above  IV  has  the  constitution  which 
had  already  been  shown  to  be  that  of  terpinolene.  A  hydrocarbon 
having  the  structure  represented  by  II,  A3-1(7>-p-menthadiene,  has 
been  synthesized  by  Wallach  70  from  sabina  ketone  and  found  to  yield 
a  tetrabromide  melting  at  154°-155°,  and  boiling  at  173°-174°.  It  is 

«  Wallach,  Ann.  357.  64   (1907). 

"Ann.  357,  68   (1907)  ;  362,  287    (1908). 


338       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

therefore  not  present  in  ordinary  "terpinene"  boiling  at  179°-182° 
and  which  does  not  yield  a  crystalline  tetrabromide.  The  constitution 
of  "terpinene"  therefore  resolves  itself  into  I  or  III,  or  a  mixture  of 
these  two  hydrocarbons. 

On  oxidizing  ordinary  terpinene  with  permanganate,  a  a'-dioxy- 
a-methyl-a'-isopropyladipic  acid,  melting-point  189°  is  formed.  This 
acid  can  only  be  derived  from  A1-3-p-menthadiene. 


OH 


a-terpinene  erythrite         adipic  acid  derivative 

The  structure  of  this  acid  has  been  proved  beyond  question  by  its 
synthesis,  in  the  following  manner, 

CH3  CH3 

CO  C  — OH. 

H2C  +2HCN >        H2C          CN 

H2C  H2C          CN 

CO  C\ 

I  |     OH. 

C3H7  C3H7 

followed  by  hydrolyzing  the  nitrile  to  the  adipic  acid  derivative.  The 
structure  of  this  acid  can  also  be  shown  by  following  the  oxidation  of 
terpinenol-  (4)  CH3 


THE  PARAMENTHANE  SERIES 


which   also  yields  this  adipic   acid  derivative.71    Further  oxidation 
yields  dimethyl-acetonylacetone  whose  dioxime  melts  at  137°. 

Additional  evidence  of  the  presence  of  A1  •  3-p-menthadiene  in  "ter- 
pinene" has  been  furnished  by  the  conversion  of  terpinene  nitrosite  to 
carvenone,  first  by  reducing  the  nitrosite  in  alcohol  solution  by  zinc,72 
and  later  with  particularly  good  yields,  by  reducing  the  nitrolamine 
by  zinc  and  acetic  acid.73 

CH3 
•H 

.OH 


terpinene 
nitrolamine 


carvenone  oxime 


carvenone 


In  the  investigation  of  terpinene  from  various  different  sources  or 
made  in  different  ways,  it  was  observed  that  those  specimens  which 
give  good  yields  of  the  a  a'-dioxy-a  a'-methylisopropyladipic  acid, 
melting  at  189°,  also  give  good  yields  of  the  above  crystalline  nitro- 
site.7* On  the  other  hand  it  has  been  noted  that  specimens  which  yield 
little  or  no  nitrosite  also  yield  very  little  of  the  adipic  acid  derivative 
melting  at  189°. 

The  presence  of  A1  •  4-p-menthadiene  in  terpinene  was  made  prac- 
tically certain  by  the  discovery  of  Gildemeister  and  Miiller 75  that  one 
of  the  oxidation  products  was  isopropyl  tartronic  acid.  This  specimen 
of  terpinene  was  isolated  from  ajowan  oil  and  Gildemeister  and  Miiller 
were  unable  to  isolate  a  crystalline  nitrosite,  nor  could  they  detect  the 
adipic  acid  derivative  among  the  oxidation  products.  All  experience 
with  terpinene,  particularly  as  brought  out  by  Wallach's  extensive 
investigations,76  indicate  that  "terpinene"  is  a  mixture  containing  vary- 
ing proportions  of  the  two  isomers,  which  Wallach  designates  as  a  and 
y-terpinene  (see  above).  Auwers  has  studied  the  terpinene  question 
from  the  standpoint  of  their  physical  properties,  particularly  the  re- 

71  Wallach,  Ann.  362,  266  (1908). 

"Amenomiya,  Ber.  38,  2730    (1905). 

"Wallach,   Ber.  40,  582    (1907). 

"Wallach,  Ann.  374,  229,  250   (1910). 

75  Schimmel  &  Co.  Semi-Ann.  Rep.  1909  (2),  16. 

'•Ann.  362,  261,  285   (1908)  ;  368,  13   (1909)  ;  574,  224   (1910). 


340       CHEMISTRY  OF  THE  NON-BENZENOID- HYDROCARBONS 

fractive  index.  In  accord  with  Wallach's  findings,  Auwers  showed 
that  a  terpinene  having  a  particularly  high  refractive  index,  as  would 
be  expected  in  the  case  of  a-terpinene,  also  gave  a  very  large  yield  of 
crystalline  nitrosite  and  the  adipic  acid  derivative.  Wallach  believes 
that  the  preparation  of  strictly  pure  terpinenes,  terpinolene  and  the 
phellandrenes  is  impossible.77 

Carvenene  is  probably  an  impure  a-terpinene.  It  was  so  named  by 
Semmler,78  who  prepared  it  from  carvenone  by  the  action  of  PC15 
followed  by  reduction.  According  to  Semmler,  alcoholic  sulfuric  acid 
converts  carvenene  to  an  isomeric  hydrocarbon  isocarvenene  which  he 
considers  is  identical  with  (3-terpinene.  Auwers  does  not  agree  with 
Semmler  as  to  the  supposed  purity  of  carvenene  and  claims  that  it  is 
not  identical  with  a-terpinene  which  Auwers  made  from  0-cresol. 

Henderson  and  Sutherland 79  have  made  what  appears  to  be  mainly 
a-terpinene  by  reducing  thymohydroquinone  to  2 . 5-dioxy-p-menthane 
and  decomposing  this  with  removal  .of  two  molecules  of  water.  Their 
a-terpinene  showed  a  boiling-point  of  179°,  specific  gravity  about 
0.840  and  refractive  index  1.4779.  Pickles 80  isolated  a  terpene  "origa- 
nene"  from  the  volatile  oil  of  Origanum  hirtum,  which  he  considers  is 
probably  a-terpinene. 

Crithmene. 

This  terpene  is  mentioned  in  connection  with  the  terpinenes  since 
it  yields  terpinene  dihydrochloride  on  treating  with  hydrogen  chloride. 
It  is  contained  in  the  volatile  oil  of  Crithmum  maritimum.81  Its  boil- 

20° 

ing-point  is  178°-179°,  specific  gravity,  0.8658,  n~- 1.4806.    It  does 

not  yield  a  crystalline  tetrabromide,  the  nitrosite  melts  at  89°-90° 
and  the  nitrosate  at  104°-105°.  It  yields  two  nitrosochlorides  which 
can  be  distinguished  by  their  different  crystal  forms,  although  the 
melting-points  are  very  close  together,  101°-102°  and  103°  and  104°. 
The  discoverers  have  suggested  that  crithmene  is  probably  A1**7*-**8)- 
p-menthadiene. 


"Fairly  pure  a-terpinene  has  been  synthesized  by  Wallach,  Ber.  tf,  2404  (1909). 

19  J.  TChem.  Soc.  97,  1616   (1910). 

80  J.  Chem.  Soc.  93,  862  (1908). 

81  Fransesconi  &  Sernagiotto,  AtU  accad.  Lincei.  1913.  231,  312 :  Delepine  &  Belsunce 
Butt.  soc.  chim.  (4)  S3,  34  (1918). 


THE  PARAMENTHANE  SERIES  341 

CH2 


H2C  "  CH2 

H2C  CH2 

\   / 
C 


CH3        CH3 

crithmene 

The  Oxides.    1.8-Cineol,  1 . 4-Cineol,  Pinol  and  Ascaridol. 

These  oxides  of  the  terpene  series  are  usually  described  without 
reference  to  other  intramolecular  ethers,  or  oxides,  of  the  non-ben- 
zenoid  hydrocarbons.  Unfortunately  the  number  of  such  organic 
oxides,  to  use  the  customary  term,  which  are  known,  is  so  small  that 
it  is  not  possible  to  show  such  close  relationships  between  those  which 
happen  to  have  been  first  prepared  from  the  terpenes,  and  those  pre- 
pared from  other  non-benzenoid  cyclic  or  open  chain  hydrocarbons,  as 
might  be  desired. 

In  the  first  place  it  may  be  noted  that  the  ethylene  oxide  ring  is 
considerably  less  stable  than  the  tri-carbon  ring  in  cyclopropane  and 
its  derivatives.  Thus  ethylene  oxide  reacts  with  water  on  heating 
to  give  glycol  and  this  reaction  is  catalyzed  by  a  trace  of  a  mineral 
acid.82 

CH2  CH2OH 

0  +  H20  - 
,  CH2OH. 

Oxides  of  this  type  have  been  carefully  studied  in  the  case  of  the 
oxides  of  ethylene,  propylene,  the  butylenes,  amylenes  and  hexylenes. 
They  react  with  hydrogen  chloride  with  considerable  energy,  forming 
the  chlorohy drins ;  with  ammonia  to  form  the  corresponding  amino 
alcohols,  with  nascent  hydrogen  to  give  alcohols  and  with  a  variety  of 
other  substances,  as,  for  example,  sodium  malonic  ester, 

«  Henry,  C&mpt.  rend.  W,  1404   (1907). 


342       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

CH2  Na  CH2ONa 

|      >o+       >C.(C02C2H5)2 >| 

CH2  H  CH2CH(C02C2H5), 

The  greater  instability  of  the  ethylene  oxide  ring  as  compared  with 
the  tri-carbon  ring  is  brought  out  in  the  case  of  isobutylenoxide 
(CH3)2C CH2,  which  reacts  with  water  to  form  the  glycol  merely 

0 

on  shaking  together  with  water  at  ordinary  temperatures.  (The  group 
(CH3)2C<  in  cyclopropane  usually  results  in  greater  stability.)83 
As  with  carbocyclic  rings  a  great  increase  in  stability  is  noted,  com- 
pared wth  ethylene  oxide,  when  the  oxide  ring  contains  five  or  six 
atoms.  Thus  diethylene  oxide  CH2  — 0  — CH2  is  the  principal 

CH2  —  0  —  CH2 

product  resulting  when  ethylene  glycol  is  distilled  with  4  per  cent 
aqueous  sulfuric  acid;  in  the  same  manner,  but  with  smaller  yields, 
1.8-terpin  yields  ordinary  cineol  and  1.4-terpin  yields  1.4-cineol. 
Diethylene  oxide,  in  contrast  to  ethylene  oxide,  yields  a  series  of  well- 
defined  addition  products  84  of  the  type  which  Baeyer  suggested  were 
derivatives  of  quadrivalent  oxygen;  the  sulfate,  C4H802.H2S04  melts 
at  101°,  the  dibromide  C4H402Br2  melts  at  60°,  etc.  When  the  con- 
stitutions of  these  two  substances  are  compared  it  is  apparent  that 
the  reason  for  the  greater  stability  of  diethylene  oxide  is  the  hexatomic 
ring. 

CH2  CH2  — 0  — CH2 

I      >0  |  | 

CH2  CH2  — 0  — CH2 

diethylene  oxide. 

In  connection  with  the  stability  of  diethylene  oxide  its  comparatively 
high  melting-point  +  9.5°,  and  boiling-point  100°-101°  are  significant. 
If  the  valence  directions  of  quadrivalent  oxygen  are  in  the  directions 
of  the  four  corners  of  a  regular  tetrahedron  as  we  assume  to  be  the 
case  in  the  carbon  atom,  then  we  should  expect  a  close  parallel  with 
non-benzenoid  carbocylic  substances,  as  regards  stability  and  ease 
of  formation  and  rupture.  Derick  and  Bissell 85  have  called  attention 

"Ingold,  J.  Chem.  Soc.  119,  305  (1921). 

"Paterno  &  Spallino,  Gaez.  chim.  Ital.  37  (1),  106  (1907)  ;  Faworski,  Chem.  Zentr. 


19ffl   (I),  16. 


Am.  Chem.  Soc.  1916,  2478. 


THE  PARAMENTHANE  SERIES  343 

to  the  fact  that  trimethylene  oxide  CH2CH2CH2O,  which  contains 

four  atoms  in  the  ring  is  markedly  more  stable  than  ethylene  oxide. 
[The  stereochemistry  of  oxygen  has  been  very  little  studied.  There 
would  seem  to  be  no  reason  why  substances  containing  asymmetric 
oxygen  cannot  be  resolved  into  optically  active  forms,  possibly  by 
Pasteur's  method  of  mechanically  picking  out  crystals  of  opposite 
hemihedral  development.]  It  has  been  noted86  that  1.4  and  1.5- 
glycols  and  their  oxides  behave  in  a  manner  markedly  different  from 
the  1.2-glycols.  The  former  are  readily  converted  into  their  oxides 
of  five  and  six  membered  rings  respectively  by  heating  with  60  per 
cent  sulfuric  acid  and  these  oxides  are  quite  stable  to  water;  in  fact, 
they  can  be  heated  with  water  to  200°  several  hours  without  forming 
glycols.  It  should  be  pointed  out  that  their  behavior  is  strictly 
parallel  to  the  behavior  of  the  better  known  oxides,  cineol  and  pinol. 

Up  to  the  present  time  the  only  oxides  whose  synthesis  has  been 
attempted  with  the  idea  of  industrial  utilization  are  the  simpler  1.2 
oxides,  i.e.,  ethylene  oxide  for  the  manufacture  of  phenylethyl  alcohol 
by  the  Grignard  reaction,87 

C6H5MgBr  +  (CH2)20 »  C6H6CH2CH2OH, 

and  other  organic  preparations,88  and  the  1.2  oxides  of  butylenes  and 
amylenes  which  have  been  proposed  as  solvents  for  cellulose  esters.89 
However,  the  1.4  and  1.5  oxides  are  quite  stable  and  should  prove 
industrially  valuable  if  they  could  be  made  economically. 

Tetramethylene  oxide.        CH.,  —  CH2  boils  at  67°  and  is 

I  >0 

PITT  OUT 

U±12  —  v-;.tl2 

easily  soluble  in  water.  It  is  not  reacted  upon  by  water  at  150°  but 
is  attacked  by  fuming  hydrobromic  acid. 

1  A-Oxidopentane.        CH2  —  CH  —  CH3         is  a  liquid  of  agree- 


1 
C 


H2  —  CH2 

able  ethereal  odor  boiling  at  77°-78°  and  soluble  in  10  parts  of  water 
at  ordinary  temperatures.  It  can  be  made  by  heating  the  1.4-glycol 
with  60  per  cent  sulfuric  acid  or  by  the  action  of  caustic  alkali  on  the 

M  Petrenko-Kritschenko  &   Konschin,  Ann.   Sl,2,   51    (1905). 

87  Grignard,  Compt.  rend.  136,  1260  (1903)  ;  Altwegg,  U.  S.  Pat.  1,315,619.     Accord- 
ing to  the  writer's  experience  this  reaction  gives  yields  75  to  80  per  cent,  of  the  theo- 
retical ;  ethylene  oxide  is  best  made  by  solid  caustic  soda  on  nearly  anhydrous  ethylene 
chlorohydrin. 

88  Cf.    Soc.   chim.    du   Rhone,    Brit.    Pat.    128,552;    128,553;    128,554    (1919),  —  for 
aminobenzoic  acid  derivatives;  Brit.  Pat.  128,911   (1919)    for  chloroethyl  esters;  Brit. 
Pat.  128,908  (1919)  for  ethanolamines  and  aminophenol  ethers. 

"Walker,  U.  S.  Pat.  972,952. 


344       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

corresponding  chlorohydrine.    The  dimethyl  derivative  is  a  product  of 
the  action  of  sulfuric  acid  on  diallyl, 

CH2CH  =  CH2  CH2CH  —  CH3 

>  I  >0  boiling-point  90°-92° 

CH2CH  =  CH2  CH2CH  —  CH3 

1 .6-Oxidopentane  (Pentamethylene  oxide).90 

CH2  — CH2 

CH2  0 

CH2  — CH2 

can  be  obtained  by  heating  1 . 5-dibromopentane  with  water  at  100° 
or  from  the  glycol  by  the  sulfuric  acid  method.  The  oxide  boils  at 
81°-82°.  The  same  methods  of  preparation  have  proven  successful 
in  the  conversion  of  1.4  and  1.5-dihydroxy-n.hexane  91  to  the  corre- 
sponding oxides.  Most  of  the  glycols  containing  six  or  more  carbon 
atoms  are  quite  difficult  to  prepare  and  since  interest  in  them  is  so 
narrow,  they  are  not  described  here.  The  above  examples,  however, 
are  given  in  support  of  the  general  thesis  of  the  present  volume,  that 
the  chemistry  of  the  so-called  hydro-aromatic  hydrocarbons  is  ration- 
ally a  part  of  the  larger  division  of  non-benzenoid  hydrocarbons. 
*  Cineol  is  the  name  given  by  Wallach  and  Brass 92  to  the  substance 
C10H180,  boiling-point  172°,  which  they  isolated  from  the  volatile  oil 
of  wormseed,  "Oleum  cince"  from  Artemisia  maritime,  L.  It  was  also 
shown  that  "cajeputol"  from  cajeput  oil  and  "eucalyptol"  were  identi- 
cal with  cineol.  Gladstone  had  shown  that  cineol  could  be  distilled 
over  metallic  sodium  without  change  and  Hell  and  Ritter 93  obtained 
an  addition  product  with  hydrogen  chloride  and  accordingly  suggested 
that  the  oxygen  was  bound  as  in  ethylene  oxide,  but  recognized  that 
cineol  is  much  more  stable  than  ethylene  oxide. 

The  following  additive  compounds  have  been  prepared  from  cineol, 
(C10H180)2.HC1;  (C10H180)2.Br2;  C10H18O.Br2;  (C10H180)2.I2; 
C10H18O.HBr;  C10H18O.H3P04;  C10H18O.H3As04,93  also  well  crys- 
tallized products  with  hydroferricyanic  and  hydroferrocyanic  acids, 
a  and  (3-naphthol,94  iodol  and  resorcin.  This  property  is  utilized  for 
the  detection  and  quantitative  estimation  of  cineol,  methods  based 

90  Hochstetter,  Monatsh.  23,  1073   (1902). 

"Franke  &  Lieben,  J.  Chem.  Soc.  Abs.  1913.  I,  491. 

•"Ann.  225,  291    (1885). 

M  Merck,   German   Pat.   132,606. 

"Henning,  German  Pat.  100,551;  Chem.  Zentr.  1899  (1),  764. 


THE  PARAMENTHANE  SERIES  345 

upon  the  reaction  with  phosphoric  acid  and  with  resorcin  bejng  most 
favored  for  quantitative  estimation.'5 

Composition  of  Product"  Melting-Point 

OoHuO.HBr    .........................................      56. 

doH.80.CJ.NH.  (iodol)     .....  >  ........................     112. 

(C10HMO)2.C9H4(OH)2  (resorcin)     ......................      80. 

(CioH18),.C«H4(OH),(hydroquinone)    ..................     106.5 

aHsOH    .....................................        8. 

e^OH.CH,  (orthocresol)     ...................      50. 

.  thymol    ......................................        4.5 


Baeyer97  first  pointed  out  that  these  addition  products,  which  are 
generally  decomposed  easily  into  their  original  constituents,  are  prob- 
ably derivatives  of  quadrivalent  basic  oxygen.  Baeyer  regarded  the 
comparatively  stable  compound  of  ethyl  ether  and  magnesium-alkyl 

X 
halides  as  "oxonium"  compounds  of  the  constitution  (C2H5)20< 

MgR 
but  more  recent  investigations  point  to  the  structure  C2H5  MgX 


C2H5          R 

which  was  proposed  by  Grignard.  When  cineol  is  used  as  a  reaction 
medium  instead  of  ether,  the  reaction  of  magnesium,  ethyl  iodide  and 
cineol  takes  place  with  almost  explosive  violence  unless  the  cineol  is 
diluted  with  benzene.98  When  cineol  is  added  to  a  solution  of  mag- 
nesiumethyl  iodide  in  ethyl  ether,  the  ethyl  ether  is  displaced  and  the 
cineol  compound,  (C10H180)2MgC2H5I,  is  precipitated.  When  this 
compound  is  decomposed  by  dilute  acids  cineol  is  almost  quantitatively 
regenerated,  but  if  the  complex  is  heated  to  170°-190°  and  then  care- 
fully decomposed  by  cold  dilute  acids,  a-terpineol  is  formed.  If  the 
conditions  are  reversed  and  magnesium-ethyl-bromide  is  poured  into 
cineol,  an  oil  is  produced  the  products  of  hydrolysis  of  which  have  not 
been  investigated.  l-Ethyl-p-menthanol(8)  should  be  formed  if  the  re- 
action product,  like  many  other  Grignard  ether  complexes  which  have 
been  investigated,  is  capable  of  decomposing  in  several  ways.  In  the 
case  of  ethylene  oxide  and  phenyl  magnesium  bromide,  phenyl  ethyl 
alcohol  is  the  principal  product.  Cineol  reacts  with  acetic  anhydride 
in  the  presence  of  metallic  chloride  ZnCl2  or  FeCl3  to  form  terpinyl 
acetate  and  terpin  diacetate." 

•8Cf.    Parry,    "Chemistry   of   Essential    Oils,"    Ed.    3.   Vol.    I,   321,    Vol.    II,    256; 
Gildemeister,  "Aetherische  Oele,"  Ed.  2,  Vol.  I.  547. 
"Belluci  &  Grass!,  Chem.  Zentr.  1914   (1),  884. 
"  Ber.  S4,  2679   (1901)  ;  35,  1201   (1902). 
MPickard  and  Kenyon,  J.  Chem.  Soc.  91,  896   (1907). 
•»  Knoevenagel,  Ann.  402,  111   (1919). 


346       CHEMISTRY  OP  THE  NON-BENZENOID  HYDROCARBONS 

The  constitution  of  cineol  is  clearly  indicated  by  its  formation 
from  1.8-terpin  by  oxalic  acid  and  other  dehydrating  agents,  by  the 
formation  of  dipentene  dihydrochloride  from  cineol  by  the  action  of 
hydrogen  chloride  (in  acetic  acid),  by  the  absence  of  a  double  bond 
and  the  absence  of  a  carbonyl  group.  Cineol  was  formerly  regarded 
as  the  1.4  oxide  but  when  a-terpineol  was  shown  to  be  A^p-men- 
thenol  (8)  and  ordinary  terpin  to  be  the  1.8  derivative,  the  constitu- 
tion attributed  to  cineol  was  revised  to  accord  with  these  facts.  Hot 
permanganate  solution  oxidizes  cineol  to  cineolic  acid,  which  sub- 
stance retains  the  1.8  oxide  grouping. 


cineolic  acid,  M.-P.  197 ( 


Cineol  occurs  in  the  volatile  oil  of  many  species  of  eucalyptus  and 
the  commercial  valuation  of  eucalyptus  oils  is  usually  determined  by 
their  cineol  content.  Commercial  oils  are  derived  from  a  number  of 
different  species  and  earlier  references  to  the  essential  oil  of  Eucalyp- 
tus globulus  undoubtedly  refer  to  the  mixed  oil  from  several  species. 
The  genuine  oil  of  Eucalyptus  globulus  contains  50  to  70  per  cent  of 
cineol,  the  balance  being  d-a-pinene,  and  minor  percentages  of  a  ses- 
quiterpene  alcohol  which  has  been  named  globulol,  an  unidentified 
terpene  and  very  small  proportions  of  butyric,  valeric  and  caproic 
aldehydes.  R.  T.  Baker  and  H.  G.  Smith  have  made  a  systematic 
survey  of  the  various  species  of  eucalyptus  and  the  volatile  oils 
derived  from  them,  the  results  of  which  have  been  published  in  a 
comprehensive  monograph  10°  and  in  a  series  of  papers  in  the  Journal 
of  Proceedings,  Royal  Society  of  New  South  Wales.  Baker  and  Smith 
find  58  species  yielding  oils  whose  principal  constituents  are  cineol  and 
pinene,  14  in  which  pinene  and  sesquiterpenes  are  the  chief  compo- 
nents, 9  which  contain  notable  percentages  of  a  new  aldehyde  "aro- 

"x>"Eucalypts'of  Tasmania,  "  1912;  J.  Soc.  Chem.  Ind.  32,  710   (1913). 


THE  PARAMENTHANE  SERIES 


347 


madendral,"  101  33  species  which  yield  oils  characterized  by  phellan- 
drene  and  piperitone  (q.v.),  and  several  other  species  whose  oils  differ 
markedly  from  those  above  mentioned.102 

Cineol  crystallizes  on  chilling  the  fraction  boiling  at  174°-178° 
from  good  eucalyptus  oil  and  its  isolation  in  this  way  is  comparatively 
easy,  though  naturally  not  quantitative. 

A  ketone  derivative  of  cineol  has  been  made  from  a-terpineol  by 
first  preparing  a-terpineol  nitrosochloride,  treating  this  with  hydrox- 
ylamine,  thus  replacing  Cl  by  — NH.OH.  and  hydrolyzing  the 
resulting  product  by  water.103 

:H,  CH,  CH, 


CH}  -  tH3 

a-terpineol 

1.4-Cineol:  This  isomer  of  ordinary  cineol  has  not  been  found 
in  nature,  but  was  discovered  by  Wallach  as  one  of  the  products  of 
the  dehydration  of  1.4-terpin  by  oxalic  acid.104  It  boils  at  172°  but 
does  not  crystallize  on  cooling  to  — 15°.  It  is  quite  stable  to  per- 
manganate solution. 

Ascaridol  is  one  of  the  most  remarkable  organic  compounds  known. 
It  was  discovered  by  Schimmel  &  Co.  in  1908 105  in  the  volatile  oil  of 
American  wormseed  or  Chenopodium  ambrosioides,  L.,  var  anthel- 
minticum.  It  was  found  to  contain  two  atoms  of  oxygen  and  on  heat- 
ing to  130°-150°  decomposes  with  explosive  violence.  On  reducing 
by  Paal's  method,  four  atoms  of  hydrogen  are  taken  up  and  one  of 
the  stereoisomeric  forms  of  1.4-terpin  are  formed.  This  1.4-terpin, 
melting  at  116°-117°,  is  regarded  by  Wallach106  as  the  cis  form. 
(The  identity  of  this  terpin  was  clearly  shown  by  its  conversion  to 
terpinene  dihydrochloride  and  by  its  decomposition  to  1.4-cineol.) 


101  J.  Proc.  Roy.  Soc.  N.  S.  W.  1900,  1. 

102  An   excellent   review   of   the   eucalyptus   oils   is   given   in   Parry, 
Essential  Oils,"  Ed.  3,  Vol.   I,   pp.  319-358. 

103Cusmano  &  Linari,  Gazz.  &   (1),  1   (1912). 

104  Ann.  392,  62    (1912). 

105  Reports,  1908  (1),  108. 
10*Ann.  S92t  59   (1912). 


'Chemistry   of 


348      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

The  absence  of  double  bonds  and  hydroxyl  or  carbonyl  oxygen,  its 
peroxide-like  properties  and  its  relation  to  1.4-terpin,  indicates,  in 
Wallach's  opinion,  a  peroxide  structure.  Nelson107  first  showed  the 
peroxide  character  of  ascaridol  but  suggested  that  the  two  peroxide 
oxygen  atoms  connected  the  2.5  positions.  By  treating  with  ferrous 
sulfate  solution  in  the  cold  two  glycols  C10H1803,  melting  at  62.5°-64° 
and  103°-104°  are  obtained.  Heating  the  higher  melting  glycol  with 
dilute  sulfuric  acid  yields  p-cymene.  According  to  Wallach's  consti- 
tution for  ascaridol,  the  erythritol  C10H2004,  melting  at  128°-130° 
should  yield  a,  a'-methyl-isopropyl-a,  a'-dihydroxyadipic  acid,  and 
Nelson  obtained  an  oxidation  product  of  this  acid,  i.e.,  2-methylhep- 
tane-3.6-dione.  By  acid  permanganate  Nelson  has  split  the  acid 
C10H1606,  from  the  lower  melting  glycol,  to  2-methyl-heptane  -3.6- 
dione.  Nelson  suggests  the  following  relationships. 


CH 


ascaridol 


erythritol 


glycol 


1 .4-cineolic  acid 


Ascaridolic  acid,  which  possesses  the  structure  of  a  1. 4-cineolic  acid, 
was  resolved  by  Nelson  by  means  of  its  cinconidine  salt  to  the  d.  and 
I.  forms. 

The  physical  properties  of  ascaridol  are,  boiling-point  83°  under 

20° 
5  mm.  pressure,  sp.  gr.  (20°)  1.008,  [a]      —4°  14  and  n_  1.4731. 

Pinol:  The  resemblance  of  pinol  to  the  two  cineols  is  indicated 
by  its  chemical  behavior  and  its  methods  of  preparation.  Thus  terpi- 
neol  dibromide,108  on  treating  with  aniline  or  alcoholic  alkali  loses  one 
molecule  of  hydrogen  bromide  to  form  an  unsaturated  bond  and  loses 
a  second  molecule  of  HBr  after  the  fashion  of  the  bromo-hydrines 
and  chlorohydrines  to  form  the  oxide  pinol. 

1OT  J.  Am.  CTiem.  Soc.  33,  1404   (1911)  ;  35,  84   (1913). 
108Wallach,  Ann.  253,  254,  261    (1889). 


THE  PARAMENTHANE  SERIES 


349 


a-terpineol  dibromide          pinol 

Like  cineol  the  oxide  ring  is  quite  stable  but  the  double  bond 
reacts  normally,  being  oxidized  by  permanganate  to  terebinic  acid, 
adds  bromine  to  form  pinol  dibromide,  melting-point  94°,  gives  a 
nitrosochloride,  etc.  The  odor  of  pinol  resembles  cineol  and  camphor. 
With  mineral  acids  it  readily  yields  cymene.  Its  physical  properties 

20°  20° 

are  as  follows,  boiling-point  183°-184°,  d 0.942,  n— -1.4714. 

When  pinol  is  treated  with  hydrogen  bromide  in  acetic  acid  solu- 
tion, the  oxide  ring  is  broken,  as  with  other  oxides,  and  so-called  pinol 
hydrobromide  is  formed,  which  on  treating  with  alkali  yields  "pinol 
hydrate," 


H 
OH 


.OH 

^ 

pinol  pinol  hydrate 

The  dibromide  of  pinol  hydrate  on  treating  with  alkali  yields  a 
dioxide,  H 


350       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


On  treating  pinol  tribromide  with  zinc  in  acetic  acid  pinolone  is 
formed.  This  reaction  has  been  a  puzzling  one  and  is  worth  noting 
as  an  instance,  now  established  beyond  question,  of  the  conversion  of 
the  six  carbon  ring  to  the  cyclopentane  ring.  Wallach  109  has  proven 
that  dihydropinolone  is  acetylisopropylcyclopentane.  Hydrogenation 
of  pinolone  yields  the  saturated  ketone  dihydropinolone,  the  constitu- 
tion of  which  has  been  shown  both  by  decomposition  studies  and  by 
synthesis,  to  be  1 . 3-acetylisopropylpentanone.  The  synthesis  is  of 
interest  as  employing  reactions  of  quite  general  application. 


H, 


AH, 


N.OH 

i 


0 


AH, 


dihydropino  lone 

The  fact  of  the  formation  of  the  cyclopentane  ring  is  thus  clearly 
established.  Wallach  suggests  an  explanation  of  this  change  which 
is  based  upon  the  conversion  of  the  glycid  group  to  a  ketone  group, 
many  examples  of  which  are  known,  particularly  as  shown  by  recent 
researches  of  Darzens.110 


H    H 


pinol  tribromide 


109  Ann.  384,  193   (1911). 

™Compt.  rend.  152,  443,  1105   (1911). 


THE  PARAMENTHANE  SERIES 


351 


CO 
-CH 


or 


pinolone 

As  mentioned  above,  chlorohydrines  yield  oxides  when  treated 
with  caustic  alkali.  Slawenski  m  has  made  pinol  and  pinol  hydrate 
by  the  action  of  caustic  potash  upon  the  chlorohydrin  of  terpineol 
(the  latter  substance  being  made  by  the  direct  addition  of  hypochlor- 
ous  acid  to  terpineol).  The  formation  of  pinol  and  pinol  hydrate 
shows  that  the  chlorine  is  in  position  6. 

An  oxide  of  the  diterpene  series  has  been  discovered  in  Java,  citro- 
nella  oil.  The  oxide,  C20H340,  boils  at  182^-183°  (at  12  mm.).  It 
contains  two  double  bonds  and  is  reduced  by  hydrogen  and  platinum 
black  to  C20H380:  it  yields  a  monohydrochloride  melting  at  107.5°. 
When  citronellal  is  heated  with  oxalic  acid,  one  of  the  products  is  an 
isomeric  oxide  C20H340.112 

Other  Alcohols  of  the  Paramenthane  Series. 

It  is  evident  that  by  the  partial  decomposition  of  ordinary  terpin 
or  terpin  hydrate,  four  isomeric  terpineols  can  theoretically  be  pro- 
duced, i.e., 


H. 


a- terpineol 


fi-terpineol 


I  Inactive  M.-P.  35°      M.-P.  32° 
\Active  M.-P.  37°-38° 


y-terpineol          b-terpineol 
M.-P.  69°-70°    (unknown) 


™Chemik.  Polski,  15,  97   (1917)  ;  Chem.  Ate.  IS,  887   (1919). 
112Semmler,  Ber.  47,  2077  (1914)  ;  Spornitz,  Ber.  tff  2478  (1914). 


352       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

a-Terpineol  has  been  described  in  the  foregoing  pages  on  account 
of  the  importance  of  its  constitution  to  the  structure  of  the  related 
substances  of  this  series. 

$-Terpineol  is  a  constituent  of  commercial  terpineol118  made  by 
the  partial  decomposition  of  terpin  hydrate.  It  has  not  been  found 
in  nature.  Its  physical  properties  are  as  follows,  melting-point 
32°-33°,  boiling-point  209°-210°,  d150  in  supercooled  state  0.923, 

20° 

1.4747.    Its  phenylurethane  melts  at  85°,  the  nitrosochloride  at 


n 


_ 


1030,11*  the  nitrolaniline  derivative  at  110°  and  the  nitrolpiperidine 
derivative  at  108°. 

(3-Terpineol  was  made  synthetically  by  Perkin,115  in  a  manner 
which  clearly  confirms  its  structure.  Incidental  to  the  synthesis  of 
a-terpineol,  described  above,  a  small  amount  of  hydroxyisopropyl- 
cyclohexane-4-one  was  formed,  which  ketone  was  dehydrated  in  the 
usual  manner.  When  the  resulting  unsaturated  ketone  was  treated 
with  magnesium-methyl  iodide,  |3-terpineol  was  formed. 


^-terpineol 


The  decomposition  of  (3-terpineol  by  oxidation  has  been  studied  by 
Stephan  and  Helle116  and  by  Wallach.117  One  of  the  products  of 
oxidation,  l-methyM-acetyl-A^cyclohexene  has  been  utilized  by 
Wallach118  for  the  preparation  of  a  number  of  saturated  and  un- 


&  C°*  Semi'Ann>  ReP-  1901 


m  Wallach,  Ann.  345,  128   (1903). 
118  «/.  Chem.  Soc.  85,  659   (1904). 
118Z/oc.  cit. 

111  Ann.  S24,  88   (1902). 
™Ann.  klk,  202   (1918). 


Stephan  &  Halle,  Ber.  35,  2147 


THE  PARAMENTHANE  SERIES  353 

saturated   alcohols.    Thus   magnesium-ethyl   iodide   yields   homo-a- 
terpineol 


- 

CH8-/  >C(OH)< 

X  / 


CH 


Nascent  hydrogen  reduces  the  carbonyl  group  and  when  the  result- 
ing product  is  treated  with  dilute  sulfuric  acid  1.8-dihydroxy-l- 
methyl-4-ethylcyclohexane,  melting  at  94°,  is  formed.  Two  other 
1.8-terpins  were  described  in  the  same  paper,  i.e.,  addition  of  water 
to  homo-a-terpineol  yields 

HO  -  CH3 


v 


C(OH)< 


CH3  -  C2H 

melting-point  65°-67°,  and  secondly  hydration  of 


//  -  v 
C2H5-<f  >C(OH)< 

N  -  /  CH3 

by  dilute  acids  gave  the  corresponding  1.8-terpin,  crystallizing  with 
one  molecule  of  water,  melting  at  75°-76°. 

y-Terpineol  has  not  been  found  in  nature,  but  is  one  of  the  minor 
reaction  products  when  ordinary  1.8-terpin  is  partially  decomposed 
by  oxalic  or  phosphoric  acids.  It  was  prepared  by  Baeyer  incidental 
to  his  investigation  of  the  constitution  of  terpinolene  (q.v.).  It  is 
characterized  by  its  relatively  high  melting-point,  69°-70°,  and  its 
blue  nitrosochloride  melting  at  82°.  On  heating  with  about  one 
volume  of  concentrated  formic  acid  terpinolene  results.119 

&3-p-Menthenol(8),  was  made  synthetically  by  Perkin  and  Wal- 
lach  12°  incidental  to  their  synthesis  of  A3<8(9)-p-menthadiene.  It 
melts  at  41°,  boils  at  205°  with  slight  decomposition  and  yields  a 
phenylurethane  melting  at  about  128°,  the  melting-point  varying 
somewhat  with  the  rate  of  heating  owing  to  decomposition  at  this 
temperature. 

A2-p-Af  enthenol  (  1  )  ,  is  related  to  the  phellandrenes   (q.v.).    It  is 

"'Wallach,  Ann.  368,  11    (1909). 
120  Ann.  37+,  198. 


354       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

easily  decomposed  by  dehydrating  agents  to  give  a-phellandrene.  It 
was  made  synthetically  by  Wallach121  by  the  action  of  magnesium 
methyl  iodide  on  4-isopropyl-A2-cyclohexenone.  It  boils  at  92° 

(10mm.). 

The  Terpinenols:  Several  terpene  alcohols  are  known  which  can 
be  derived  from  the  1.4-terpin  of  the  terpinene  series,  and  are  hence 
called  terpinenols.  As  in  the  case  of  1.8-terpin,  noted  above,  loss  of 
one  molecule  of  water  from  1.4-terpin  can  theoretically  lead  to  the 
formation  of  four  isomeric  alcohols. 


CH3 


OH 


Terpineol-4        Terpinenol-1  unknown          y-Terpineol 


Of  the  substances  indicated  above,  it  will  be  noted  that  IV  is  identical 
with  y-terpineol. 

Terpinenol-4  is  found  in  nature  in  a  number  of  essential  oils, 
juniper,  Ceylon  cardamon,  nutmeg  and  zedoary.122  It  is  formed  by 
the  hydration  of  sabinene  by  cold  dilute  sulfuric  acid.123  The  physi- 
cal properties  of  optically  active  terpinenol-4  are  as  follows,  boiling- 

19° 
point  209°-212°,  d        0.9265,  [a]       +25°  4',  n  —  1.4785.    It  has 

iy  D  D 

not  been  obtained  in  crystalline  form.  Both  terpinenol-4  and  terpi- 
neol-1  give  terpinene  dihydrochloride  when  treated  with  hydrogen 
chloride  in  glacial  acetic  acid,  and  also  give  1.4-terpin  on  hydra  ting 
with  cold,  dilute  sulfuric  acid,  although  this  hydration  takes  place 
much  more  slowly  than  with  a-terpineol.  The  two  terpinenols  are 
however  distinguished  by  their  oxidation  products,124  r. 

111  Arm.  559,  283    (1908). 

122  Terpinenol  —  4  is  present  in  comparatively  large  proportions  in  one  of  the 
Formosan  lauracese  closely  resembling  the  camphor  tree :  Schimmel  &  Co.  Semi-Ann. 
Rep.  1915  (2),  42. 

"Wallach,  Ann.  S60,  94,  97   (1908)  ;  362,  279    (1908). 

«*  Wallach,  Ann.  356,  210  (1907). 


THE  PARAMENTHANE  SERIES 


355 


(a) 


terpinenol-4          1.2.4. -trioxy-p-menthane  h?-carvenone 
(fr-p-menthenol  4)    M.-P.  116°-1170    (H20). 


terpinenol-1          1, 8, 4- trioxy-p-menthane  ^-menthenone 125 
M.-P.  120°-121° 


Terpinenol-1  occurs  in  commercial  terpineol  and  can  be  isolated 
from  the  forerunnings  obtained  when  large  quantities  of  crude  terpin- 
eol are  distilled  with  steam.    It  has  also  been  synthesized  by  the 
action  of  magnesium  methyl  iodide  on  A3-4-isopropyl  cyclohexenone. 
I  Its  physical  properties  126  are  as  follows,  boiling-point  208°-210°,  d 

lo 

i  0.9265,  and  n  _  1.4781. 

Dihydrocarveol,  A8<9)-p-menthenol  (2) ,  is  found  in  nature  in  oil  of 
\  caraway,  associated  with  carvone.  Its  importance  in  the  work  of 
\  determining  the  constitutions  of  limonene  and  related  substances  has 


already  been  pointed  out.  It  can  be  made  by  the  reduction  of  carvone 
by  sodium  and  alcohol,127  or  by  the  reduction  of  carvoxime  to  dihy- 
drocarvylamine  and  treating  the  latter  with  nitrous  acid.  Complete 

125  A'-P-menthenone    is    characterized    by    its    boiling-point    235°-237°,    the    oxime 
melting  at  77°-79°  and  its  semicarbazone  melting  at  210°. 
1MWallach,  Ann.  S56,  218  (1907). 
^Wallach,  Ann.  275,  111   (1893). 


356       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


reduction  yields  carvomenthol.128  The  relationships  between  the  more 
important  substances  of  this  carvone  series  may  be  indicated  as  fol- 
lows, 


"a 


carvacrol 


CH 

carveol 


dihydrocarveol     carvomenthol 

CH, 


carvotanacetone     dihydro  carvone       tetrahydro- 

carvone 


Dihydrocarveol  is  characterized  by  oxidation  by  chromic  acid  to  dihy- 
drocarvone, whose  oxime  melts  at  88°-89°  (inactive)  or  115°-116° 
(active  form),  and  by  its  physical  properties,129  boiling-point  224°, 

20° 

d        0.9368,  and  n  —  1.4836.    By  shaking  with  3  per  cent  sulfuric 
lo  D 

acid  it  is  hydrated  to  2 . 8-dioxy-p-menthane  (M.-P.  112°-113°). 

Carveol  is  one  of  the  principal  products  of  the  oxidation  of  limo- 
nene  by  air  in  the  presence  of  water.130  It  boils  at  226°-227°,  yields 
a  phenylurethane  melting  at  94°-95°,  and  a  phthalate  melting  at 
136°-137°.  Its  methyl  ether  (by  CH3ONa  on  1,2,8-tribromomen- 
thane)  boils  at  208°-212.° 

Isopulegol,  A8(9)-p-menthenol(3).  This  alcohol  is  not  found  in 
nature  but  is  readily  formed  from  citronellal  by  the  action  of  acids; 

128  Cf.  Henderson  &  Schotz,  J.  Chem.  Soc.  101,  2565   (1912). 
""Schimmel  &  Co.   Semi-Ann.   Rep.   1905    (1),   51. 
""Blumann  &  Zeitschel,  Ber.  tf,  2623    (1907). 


THE  PARAMENTHANE  SERIES  357 

when  oils  containing  citronellal  are  heated  with  acetic  anhydride  this 
aldehyde  is  almost  quantitatively  converted  into  the  acetate  of  iso- 
pulegol.  Heating  with  sodium  ethoxide131  converts  isopulegol  to 
citronellol  and  also  decomposes  it  to  acetone  and  methylcyclohexanol 
(3).  Isopulegol  is  characterized  by  oxidation  to  the  corresponding 
ketone,  isopulegone,132  which  ketone  yields  an  oxime  melting  at  121° 
(active)  and  140°  (inactive  form).  The  acetate  boils  at  104°-105° 
under  10  mm.  pressure.  Isopulegol  boils  at  91°  under  13  mm.  pressure, 
0.9154,  n  1.4729. 


Menthol,  para-menthanol(3).  This  saturated  alcohol  is  a  com- 
mon article  of  commerce.  Up  to  the  present  it  has  not  been  manu- 
factured synthetically  but  is  obtained  from  oil  of  peppermint,  par- 
ticularly Japanese  peppermint.  Peppermint  has  been  under  cultivation 
in  Japan  since  about  900  A.D.,  and  in  Europe  for  a  period  probably 
equally  long,  and,  as  is  usually  the  case  with  cultivated  plants,  there 
are  numerous  varieties  and  the  number  of  distinct  species  is  as  yet 
an  open  question.  Yet,  with  the  exception  of  oil  of  spearmint133 
which  is  characterized  by  considerable  proportions  of  carvone,  the 
various  peppermint  oils  owe  their  characteristic  flavor  and  aroma  to 
menthol  and  the  corresponding  ketone  menthone.  The  menthol  occurs 
in  these  oils  partly  free  and  partly  in  the  form  of  esters  of  acetic 
and  other  acids,  and  on  chilling  part  of  the  free  menthol  crystallizes 
from  the  oil.  The  melting-point  of  menthol  is  42.5°.  According  to 
F.  E.  Wright,134  ordinary  /.menthol  crystallizes  in  four  different  forms, 
a,  p,  y  and  6,  only  one  of  which,  the  a-form,  is  stable  between  zero  and 
its  melting-point,  42.5°.  The  other  three  forms  are  monotropic  and 
have  lower  melting  temperatures,  i.e.,  35.5°  (3,  33.5°  y>  and  31.5°  6; 
all  the  unstable  forms  invert  finally  into  the  stable  a-form.  Previous 
work  of  Schaum,135,  Pope,136  Hulett137  and  others  had  shown  the 
existence  of  at  least  two  unstable  forms,  which  investigations  were 
confirmed  and  extended  by  Wright.  Menthol  boils  at  215°-216°, 

45° 
d.  —0.881  and  when  derived  from  peppermint  is  laevorotatory.    Pick- 

181  Schimmel  &  Co.  Semi-Ann.  Rep.  1913  (2),  91. 

1S2Wallach,  Ann.  S65,  251   (1909). 

183  In  the  United  States  oil  of  spearmint  is  derived  from  Mentha  viridis  (Mentha 
spicata).  The  peppermint  oil  industry  is  very  fully  described  by  Parry,  "Chemistry 
of  Essential  Oils,"  Ed.  3,  Vol.  I,  205-231. 

134  J.  Am.  Chem.  Soc.  S9,  1515    (1917). 

188  Ann.  308,  39    (1899). 

»•«/.  Chem.  Soc.  75,  463  (1899). 

mJ.  Phj/s.  Chem.  28,  667   (1899). 


358       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

ard  and  Littlebury  1S8  made  menthol  by  the  catalytic  hydrogenation 
of  thymol,  and  by  resolution  of  the  brucine  salt  of  the  monomenthyl- 
phthalic  ester  ^.menthol  was  obtained  [a]  —  48.76°  and  d.menthol 

[<x]n  +  48.15°.    A  very  large  number  of  menthyl  esters  have  been 

employed  in  the  study  of  optical  activity.189 

On  oxidation,  menthol  is  converted  into  the  corresponding  ketone 
menthone,  p-menthane-3-one.  The  relationships  between  menthol 
and  menthone  have  been  made  clear  by  the  work  of  Pickard  and 
Littlebury.  A  ketone  of  this  structure  should  exist  in  two  stereo- 
isomeric  forms  of  the  cis  and  trans  type  and  these  have  usually  been 
referred  to  as  menthone  and  isomenthone.140  Since  each  of  these 
ketones  contains  an  asymmetric 

H          CH8  H          CH3 

V  .        •   V 

H2C          CH2  H2C          CH2 

H2C          0  =  0  H2C          C  =  0 

v  v 

/  \  /  \ 

H          CH  CH  H 


carbon  atom,  each  should  correspond  to  a  pair  of  optically  active 

isomerides,  and  when  the  carbonyl  group  is  reduced  to  >  C  <  J* 

u±i 

the  possible  number  of  optically  inactive  isomerides  is  increased  to 
four  and  the  number  of  optically  active  isomerides  to  eight.  By  the 
hydrogenation  of  thymol  in  the  presence  of  catalytic  nickel,  which 
had  been  carried  out  by  Brunei,141  a  mixture  containing  60  per  cent 
of  "menthols,"  30  per  cent  of  menthones  and  10  per  cent  of  unchanged 
thymol  is  obtained.  After  removing  the  thymol,  the  alcohols  were 
separated  by  phthalic  anhydride,  in  the  usual  manner.  The  semi-  < 
barbazones  of  the  mixture  of  menthones  proved  to  have  widely  dif- 
ferent solubilities  in  alcohols,  one  nearly  insoluble  in  cold  alcohol 

™J.  Chem.  Soc.  101,  109    (1912). 


,  . 

1905  "°  ™8  nomenclature  was  use<*  by  Aschan,  "Chemie  d.  alicyklischen  Verbindungen, 
'MCompt.  rend.  140,  252  (1905),  et  seq. 


THE  PARAMENTHANE  SERIES 


359 


and  melting  at  217°,  previously  described  by  Wallach,142  and  a  more 
soluble  one  melting  at  158°.  Fractional  crystallization  of  the  hydro- 
gen phthalate  esters  yielded  two  pure  products,  one  melting  at  177° 
and  one  melting  at  130°.  The  ester  melting  at  177°  on  hydrolysis 
yields  an  optically  inactive  menthol  melting  at  51°,  "neomenthol," 
previously  isolated  by  Beckmann.143  Hydrolysis  of  the  menthyl 
hydrogen  phthalate  melting  at  130°  yields  an  inactive  menthol  melt- 
ing at  34°,  which  can  be  resolved,  by  means  of  the  cinchonine  or 
brucine  salt,  to  ordinary  i.menthol,  melting-point  43°,  and  d.menthol, 
melting-point  43°.  These  relations  are  evidently  parallel  to  and  of 
the  same  nature  as  those  between  the  borneols,  isoborneols  and  cam- 
phors (q.v.).  The  following  diagram  summarizes  the  findings  of 
Pickard  and  Littlebury, 

Thymol, 


menthone 

semicarbazone 

M.-P.  158° 


isomenthone 

semicarbazone 

M.-P.  217° 


i-Menthol,  M.-fr.  34° 

(hydrogen  phthalate,  M.-P.  130°) 


i-neo-menthol,  M.-P.  67° 
(hydrogen  phthalate,  M.-P.  177°) 


1  -menthol 

d.  menthol     d. 

leomenthol 

1  .  neomenthol 

M.-P.  43° 

M.-P.  43° 

oil 

oil 

[a]     —  48.76° 

[a]      +48.15°     [a]      +19.6° 

[a]     —  19.6° 

D 

D 

D 

D 

\ 

\        / 

/ 

\ 

^        oxidation        /  \ 

/ 

\            /     \ 

K 

Z-menthone 

d-menthone 

By  the  hydrogenation  of  pulegone  by  the  Sabatier  and  Senderens 
method,  Haller  and  Martine144  obtained  two  menthols  which  evi- 

™Ann.  263,  272   (1908). 
143  J.  prakt.  Chem.   (2)   55,  30   (1897). 

"'Comfit,   rend,   itf,   1298    (1905).        Haller's  0-pulegomenthol   is    probably  d-neo- 
menthol  and  his   a-pulegomenthol   evidently   belongs  to  the   isomenthol   series. 


360       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

dently  are  identical  with  ^.menthol  and  d.neomenthol  described  above. 
By  electrolytic  reduction  of  menthone  in  solution  in  about  equal  parts 
of  94  per  cent  alcohol  and  75  per  cent  sulfuric  acid  a  yield  of  25  per 
cent  of  the  theory  of  menthol  has  been  reported.145  Beckmann  146  has 
described  an  isomenthol  melting  at  78°-81°,  obtained  by  the  reduction 
of  a  specimen  of  d.menthone  made  by  inverting  Z.menthone  by  90  per 
cent  sulfuric  acid. 

By  passing  synthetic  "menthol  (from  thymol)  over  copper  at  300°, 
it  is  converted  to  menthone.147 

Substituted  menthols  of  the  general  constitution  indicated  below 
have  been  made  from  menthone  by  the  Grignard  reaction,  and  by 
zinc  and  alkyl  halides, 

CH3 

CH,—  CH  —  CH2 

OH 


H2  —  CH  —  C< 

I  R 

CH3-CH-CH3 

Magnesium  cyclohexyl  bromide147  gives  the  cyclohexyl  derivative 
melting  at  92°  together  with  a  cyclohexylmenthene  boiling  at  265°. 
Methyl  iodide  and  magnesium  give  chiefly  the  methyl  tertiary  alcohol; 
but  ethyl  iodide  and  magnesium  or  zinc  yields  chiefly  a  hydrocarbon 
C12H22.148  Allyl  iodide  and  zinc  149  give  the  expected  allyl  derivative, 
boiling-point  246°-252°. 

Hallers'  reaction  has  been  employed  by  Boedtker  15°  for  the  prepa- 
ration of  alkyl  derivatives  of  menthone  in  which  the  alkyl  groups  are 
in  position  2.  Thus  ethyl  iodide  and  sodium  amide,  reacting  with 
menthone,  give  2-ethyl-p-menthanone(3)  from  which  by  reducing 
in  moist  ether  by  sodium  the  2-ethyl  menthol  was  made.  The  methyl, 
n-propyl,  isoamyl  and  benzyl  derivatives  were  prepared  in  the  same 
manner. 

The  stereochemistry  of  substances  such  as  menthone  and  menthol 
is  somewhat  involved  and  has  led  to  some  confusion  in  the  description 

"8Matsui,  J.  S&c.  Chem,  Ind.  19Z1,  162A. 

»*Ber.  42,  846   (1909). 

"TMurat,  J.  Chem.  Soc.  Abs.  100   (1),  890   (1911). 


'  Ab8'  m  (1)>  474 

^Bul.   Soc.   chim.    (4)    17,   360    (1915)  ;    Haller,    Compt.   rend.   156,   1199    (1913). 
Dimethylmenthone  --  >  dimethylmenthol,  a  liquid  boiling  at  245°-247°. 


THE  PARAMENTHANE  SERIES  361 

of  these  substances  and  their  derivatives.  It  should  be  point€d  out 
that  aside  from  cis-trans  relationships  discussed  above,  menthone  pos- 
sesses two  and  menthol  three  asymmetric  carbon  atoms. 


CH3  CH3 

I      H  |      H 

C/  C/ 

H2C          CH2  H2C          CH2 

H2C          C  =  0  H2C        *C< 
\*/  \*/     OH. 

C  —  H  C\ 

I  I      H 

CH  CH 


Theoretically,  therefore,  menthol  should  be  capable  of  existing  in 
four  spatial  configurations  of  which  each  would  have  two  optical 
antipodes  and  one  racemic  form.  Kursanov  151  finds  that  when  ordi- 
nary menthol  is  treated  with  phosphorus  pentachloride,  in  benzene 
solution,  a  mixture  of  menthyl  chlorides  is  obtained,  which  are  of 
markedly  different  stability  to  caustic  alkali.  The  stable  chloride 
reacts  with  magnesium  in  ether  to  give  a  menthene,  para-menthane,  a 
crystalline  dimenthyl  (C10H19)2  melting  at  105°-106°,  [a]  —51.42° 

(which  is  identical  with  the  dimenthyl  obtained  by  the  action  of 
metallic  sodium  on  this  chloride)  and  when  the  menthyl-magnesium 
chloride  thus  formed  is  treated  with  carbon  dioxide,  a  crystalline 
menthanecarboxylic  acid  results.  The  unstable  menthyl  chloride 
yields  a  liquid  menthanecarboxylic  acid  and  the  crude  menthyl 
chloride  consequently  must  contain  two  stereoisomers.  Kursanov 
concludes  that  only  the  carbon  atom  (3)  attached  to  the  hydroxyl 
group  in  the  original  menthol  is  inverted  by  the  reaction.  When 
Lmenthone,  corresponding  in  spatial  configuration  to  ordinary  Z.men- 
thol,  is  treated  with  90  per  cent  sulfuric  acid,  it  is  partially  inverted 
to  d.isomenthone  and  according  to  Beckmann  152  the  asymmetric  car- 
bon atom  involved  in  the  change  is  the  one  to  which  the  isopropyl 
group  is  attached. 

When  the  potassium  derivative  of  menthol  is  heated  with  phenyl 
bromide  or  iodide  the  products  are  benzene  and  menthone,  but  in  the 

151  J.  Chem.  Soc.   Abs.  108   (1),  420   (1915). 
162  Ber.  W,  846   (1909). 


362       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


presence  of  finely  divided  copper  the  reaction  gives  a  high  yield  of 
menthylphenyl  ether.  When  this  ether  is  heated  with  concentrated 
hydrochloric  acid  to  170°  this  ether  is  isomerized  to  menthyl  phenol. 
Menthol  is  relatively  very  stable  and  its  esters  can  accordingly  be 
easily  prepared.  The  benzoate,  melting-point  54°,  can  be  prepared 
by  heating  with  benzoic  acid  in  autoclave  to  170°.  Although  the 
benzoate  cannot  be  made  by  mixing  the  alcohol  with  benzoic  and 
sulfuric  acids,  the  phenyl  acetate  and  phenyl  propionate  can  be  made 
in  this  way.153  In  studying  the  action  of  esters  on  magnesium  alkyl 
halides  Stadnikow 154  found  that  magnesium  menthyl  iodide  reacts 
with  ethyl  acetate  to  give  a  practically  quantitative  yield  of  menthyl 
acetate;  ethyl  propionate  gave  an  80  per  cent  yield  of  menthyl  pro- 
pionate and  ethyl  benzoate  gave  64.6  per  cent  menthyl  benzoate. 
Tschugaeff 155  prepared  a  series  of  menthyl  esters  by  acting  upon  men- 
thol by  various  acid  chlorides  in  slight  excess.  A  great  many  esters 
of  menthol  have  been  employed  in  the  study  of  optical  activity.  The 
following  table  gives  the  boiling-point  or  freezing-point  of  a  number 
of  menthyl  esters. 

Density 
20° 
0.9359 

4°- 

0.9185 
0.9184 
0.9114 
0.9074 
0.9033 
0.9006 
0.8977 


Ester                          Melting-Point          Boiling 
Formate  PS   ° 

-Point 
(15mm.) 

(25mm.) 

(20mm.) 
°(20mm.) 
(20mm.) 
(20mm.) 
.°(20mm.) 

Acetate    

108. 
118. 
129. 
141. 
153. 
165. 
175. 

Propionate    

Butyrate 

Valerate   

n  .  Hexoate  

n  .  Heptoate   

n  .  Octoate   

Dimenthyl  oxalate 

67.    -68.° 
62. 
110. 
132. 
168. 
79. 
83. 
61. 
83. 

62.'  V  ' 

Dinienthyl  succinate    

Menthvl-H-phthalate   

Dimenthy]   phthalate    

Dimenthyl  muconate   .... 

Dimenthyl  £,  y-hydromuconate 
Dimenthyl,  a,  |3-hydromuconate 
Dimenthyl  adipate    

Menthyl  piperate   

Monthyl  ft,  y-hydropiperate  
Menthyl  a,  |3-hydropiperate  .  .  . 
Dimenthyl  malonate 

263.  ° 
270.  ° 

Menthyl   glutarate    

240-3° 
248.  °-252 
257-9° 
254.6° 
256.  °-258 

Menthyl  pimelate  

Menthyl  suberate  

Menthyl  azelate  .... 

Menthyl  sebacate 

Menthyl  benzoate 

54.5° 
.  rend.  155,  1! 
1113   (1915) 

163  Senderens  &  Aboulenc,  Compt 
154  «/.  RUBS.  Phys.-Chem.  Soc.  lit, 
™Ber.  31t  360   (1898). 

254   (1912). 
;  J.  Chem.  Soc.  A6«.  M 

975  (1915). 


THE  PARAMENTHANE  SERIES 


363 


Ester 


Melting-Point          Boiling-Point 


Menthyl  phenylacetate 

Menthyl  phenylproprionate  . . .      28.5° 

Menthyl  acetoacetate    36. 

Menthyl  propyl  acetoacetate 

Menthyl  phenyl  acetoacetate  . .      69.  ° 


205.5° 
216.  ° 
154.  ° 
162.  ° 
131-3° 


(25mm.) 
(25mm.) 
(10mm.) 
(8mm.) 
(O.lmm.) 


Density 
20° 


The  freezing-point  curves  of  menthyl  mandelate  indicate  "the 
existence  to  a  considerable  extent,  of  undissociated  racemate  in  the 
liquid  state." 186 

Ketones  of  the  Para-Menthane  Series. 

There  are  two  saturated  ketones  and  one  known  diketone  derived 
from  para-menthane. 

Menthone:  The  stereo  isomers  of  menthone  have  been  discussed  in 
connection  with  menthol.  Ordinary  menthone  isolated  from  oil  of 
peppermint  and  regenerated  from  the  semicarbazone  (melting-point 
184°),  boils  at  208°,  has  a  density  0.894,  and  refractive  index  1.4496. 

The  oxime  of  menthone  is  of  interest  on  account  of  the  fact  that 
it  undergoes  a  Beckmann  rearrangement,157  with  rupture  of  the  cyclo- 
hexane  ring,  to  give  menthoneisoxime  (by  treating  with  concentrated 
sulfuric  acid).  By  dehydrating  agents  the  isoxime  yields  mentho- 
nitrile,  which  on  reduction  yields  menthonylamine  and  from  this 
amine,  by  heating  the  nitrile  with  water,  menthocitronellol  is  formed, 
as  indicated  in  the  following  outline, 


H3 


t+H 


=NOH  I  C=0 

:H'      ^CH-^H    CH, 

CjH7 


C^OH 
"CH 

wit 

menthocitronellol 

"•Findley  &  Hickmans,  J.  Chem.  Soc.  91,  905   (1907). 
»'  Wallach,  Ann.  296,  124. 


364       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


The  reduction  of  Z.menthone  oxime  yields  a  single  menthylamine,  but 
by  heating  menthone  with  ammonium  formate  a  mixture  of  crystalline 
d.  and  Z.formylmenthylamines  C10H19NH.COH  is  formed,  which  can 
be  separated,  and  which  yields  two  isomeric  menthylamines  of  the 
cis  and  trans  types  and  from  which  a  series  of  isomeric  derivatives 
have  been  prepared.158  When  menthone  oxime  is  heated  to  220°  with 
caustic  potash  159  thymol  is  formed  together  with  about  45  per  cent 
of  the  open  chain  acid,  (CH3)2CH.  (CH2)3CH(CH3)  .CH2CO2H. 

Menthone  has  been  synthesized  by  Kotz  16°  from  (3-methyl-a-iso- 
propylpimelic  acid  in  two  ways  (1)  distillation  of  its  calcium  salt 
with  soda  lime,  and  (2),  intramolecular  condensation  of  its  ester  by 
sodium  ethoxide  after  the  manner  of  the  acetoacetic  ester  condensa- 
tion, 

CH,  CH, 


CH2  — CH  — CH2C02R 
CH2  — CH  — C02R 

i, 


CH2  —  CH  —  CH2 
CH,  — CH  — CO 
C3H7 


Another  synthesis  of  menthone  by  Wallach  and  Churchill 161  is  of 
interest.  Reformatsky's  reaction  was  employed  for  the  condensation 
of  l-methylcyclohexane-4-one  with  a-bromoisobutyrate.  The  unsatu- 
rated  acid,  derived  from  the  resulting  ester,  yields  A4<8>-p-menthene. 
Substances  containing  a  double  bond  in  this  position  rearrange  under 
the  influence  of  dilute  acids,  the  double  bond  shifting  to  the  ring,  as 
in  the  case  of  terpinolene.  In  the  present  instance  i.A3-p-menthene 
is  formed  from  which  i.menthone  was  synthesized. 

CH,  CH, 


1M  Wallach,  Arm.  Stf,  67  ;  Stf,  259. 

188  Wallach,  Ann.  389,  185. 

180  Ann.  S57,  209. 

191  Ann.  360,  26   (1908). 


THE  PARAMENTHANE  SERIES 
CH3  CH3 


365 


i  dil.acid 


&3-p-menthene 


N.OH  H 

H       J  ' 
*  nitrosochloride    k*-p-menthenone 

0 


,,H7 
i. -menthone 

In  a  study  of  the  chlorination  and  bromination  of  cyclic  ketones 
Kotz  162  finds  that  the  halogen  always  substitutes  in  an  ortho  position 
to  the  carbonyl  group.  In  the  case  of  menthone,  4-chloro  or  4-bromo- 
menthane-3-one  are  obtained,  from  which  aniline  or  aqueous  potas- 
sium carbonate  followed  by  dehydration  by  oxalic  acid,  yields  A4-p- 
menthenone.  Similarly  carvomenthone  (p.menthane-2-one)  yields 
l-chloromenthane-2-one.  Wallach  has  studied  the  conversion  of 
2.4-dibromomenthone  to  the  cyclopentane  hydroxy-carboxylic  acid. 
(Cf.  "Rearrangements.") 

Oxidation  of  menthol  by  chromic  acid 163  gives  the  ketonic  acid 

(CH3)2CH.CO.CH2CH2CH.CH2C02H.    The  same  acid  is  obtained 


CH< 


by  treating  menthone  with  amyl  nitrite  and  hydrochloric  acid  and 
hydrolyzing  the  nitrosomenthone  thus  formed.164  This  ketonic  acid 
is  also  formed  by  the  air  oxidation  of  menthone,  in  sunlight.  Sun- 
light in  the  absence  of  oxygen,  however,  decomposes  menthone  giving 
a  decoic  acid  and  an  aldehyde  165  which  is  different  from  Wallach's 
menthocitronellaldehyde,  i.  e., 


.  397;  1   (1911).     Kotz  effects  this  halogenatlon  by  diluting  the  chlorine  or 
bromine  with  air  and  adding  water  and  calcium  carbonate  to  the  ketone 
ie3  Beckrnann,  J.  Chem.  Soc.  Abs.  1896   (1),  312. 
1MBaeyer  &  Oehler,  Ber.  29.  27    (1896). 
165Ciamician  &   Silber,   Ber.  42,  1510    (1909). 


366       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 
(CH3)  2CH  .  CH  CH  .  CH2  .  CH  (CH.)  .  CH2CH0.165 

Oxidation  by  potassium  permanganate  yields  oxomenthylic  acid  (1) 
and  p-methyladipic  acid,  and  Caro's  reagent  gives  a  lactone  of  di- 
methyloctanolic  acid  (2)  , 

(1)  (2) 

CH3  CH3 

CH,  -  CH  -  CH2  CH2  -  CH  -  CH2 

I  1  I      -  >CO 

CH2-  -CO          C02H.  CH2-  -CH  -  0 

CH3  —  CH  —  CH3  CH3  —  CH  —  CH3 

Menthone  can  be  alkylated  by  Hallers'  reaction  166  (sodium  amide 
and  alkyl  halide),  the  alkyl  group  being  substituted  in  position  (2). 
One  or  both  of  the  hydrogen  atoms  in  the  CH2  group  (2),  can  be 
replaced  by  alkyl  groups.167  With  hydrazine  hydrate,  menthone 
reacts  to  form  menthylidene  hydrazine,  which  on  heating  with  caustic 
potash  loses  N2  and  gives  p-menthane.168  Menthone  condenses  with 
formic  acid  esters  (amyl  formate  and  sodium)  to  form  oxymethylene 
menthone.  Benzaldehyde  reacts  slowly  in  the  presence  of  alkalies, 
but  rapidly  with  hydrochloric  acid  to  form  benzylidenementhone 
(hydrochloride  melting  at  140°).  Reduction  of  this  compound  yields 
benzylmenthol,  M.-P.  111°-112°. 

Menthone,169  like  camphor,  carvomenthone  and  cyclohexanone, 
acts  as  a  catalyst  in  the  combination  of  sulfur  dioxide  and  chlorine 
to  form  S02C12. 

The  optical  inversion  of  Z.menthone  by  sodium  ethylate  has  been 
suggested  as  a  means  of  determining  the  per  cent  of  Z.menthone  in 
pine  oils.170 

Menthone  reacts  normally  in  the  Reformatsky  reaction,171  wi 
bromacetic  ester  and  zinc,  to  give  the  ester  of  mentholacetic  acid,  th 
free  acid  readily  losing  water  and  carbon  dioxide  to  give  homomen- 
thene  CnH20,  boiling  at  186°-187°. 


in 

. 

he 


lwBoedtker,  Bull.  soc.  chim.  Ft,  360   (1915). 

167  Holler,  Compt.  rend.  156,  1199   (1913). 

188Kizhner.     J.  Russ.  Phya.   Chem.  Soc.,  M,  1754   (1912). 

""Cusmano,  Gazz.  Chem.  Ital.  50  (2),  70   (1920). 

"°Gruse  &  Acree,  Science  44,  64  (1916).  Tubandt  [Ann.  377,  284  (1910]  shows 
that  the  rate  of  inversion  of  menthone  by  acids  is  not  proportional  to  the  H  ion  con- 
centration. The  speed  of  inversion  is  greatly  retarded  by  water. 

mWallach,  Ann.  353,  313. 


THE  PARAMENTHANE  SERIES  367 

CHS  CH3 

CH  CH 

H2C  CH2  H2C  CH2 

>  OH    >     homomenthene 

m          C  =  0        H2C  C< 

'  \      /  \      /       CH2C02H      +H20  +  C0a 

CH  CH 

C3H7  C8H7 

Normal  Menthone,  l-methyl-4-propylcyclohexane-3-one.  This 
ketone,  synthesized  by  Wallach,172  does  not  smell  like  ordinary  men- 
thone,  illustrating  the  marked  influence  of  slight  differences  of  con- 
stitution on  odor,  noted  also  in  the  case  of  unsaturated  ketones  similar 

CHa 


H2C         CH 


H2 


C         C  =  0 


AH. 


to  ionone  and  also  in  the  case  of  artificial  musk  when  the  tertiary 
butyl  group  in  Musk  Bauer  is  replaced  by  similar  alkyl  groups.  Nor- 
mal menthone  boils  at  215°-217°. 

fr-p-Menthenone,  has  been  found  in  Japanese  oil  of  peppermint 178 
and  in  one  of  the  Cymbopogon  grass  oils,  C.  senaarensis,  Chiov.174 

19° 
It  boils  at  235°-237°,  density  _  0.9375,  [a]D  1.4875.    It  forms  a 

very  sparingly  soluble  semicarbazone  melting  at  212°  and  yields  a 
dibromide  which,  by  the  action  of  aqueous  caustic  potash  and  heat, 
is  converted  almost  quantitatively  to  thymol. 

Piperitone:  This  menthenone  occurs  in  the  essential  oils  from 
several  species  of  eucalyptus,  particularly  in  E.  dives,  the  oil  of  which 
contains  40  to  50  per  cent  of  this  ketone.  It  occurs  associated  with 
the  corresponding  alcohol  "piperitol."  As  this  oil  is  available  in  large 

mChem.  Zentr.  1915  (2),  824 

™Schimmel  &  Co.  Semi-Ann.  Rep.  1910  (2),  79. 

«*  Roberts,  J.  Chem.  Soc.  1915,  1465. 


368       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

quantities  it  is  probably  only  a  question  of  a  short  time  before  men- 
thol, and  possibly  thymol,  will  be  manufactured  from  this  material; 
in  fact,  Smith  and  Penfold 175  have  reported  that  with  hydrogen  and 
catalytic  nickel  menthone  is  formed  almost  quantitatively. 

The  constitution  of  piperitone  is  not  definitely  known.  Smith 
and  Penfold  suggest  that  it  may  prove  to  be  identical  with  AA-p- 
menthenone.  They  describe  it  as  boiling  at  229°-230°  at  760  mm.  or 

106°-107°  at  10  mm.,  d2Q00.9348,  [a]D  — 40.05°  and  n— 1.4837.    It 

forms  a  semicarbazone  melting  at  219°-220°  and  an  oxime  melt- 
ing at  110°-111°.  The  most  characteristic  derivative  is  the 
compound  formed  with  benzaldehyde,  benzylidene  cU.piperitone, 
C10H14O.CH.C6H5,  melting  at  61°.  By  oxidation,  -by  boiling  with 
ferric  chloride  in  dilute  acetic  acid,  a  yield  of  thymol  corresponding 
to  25  per  cent  of  the  theory  was  obtained. 

Pulegone,  A4*8(9)-p-menthenone:  This  ketone  occurs  in  the  essen- 
tial oils  of  Mentha  pulegium  and  Hedeoma  pulegioides  and  .imparts 
its  characteristic  odor  to  oil  of  pennyroyal.  Its  physical  properties,176 
are,  boiling-point  224°  (750mm.)  or  93°-94°  at  869mm.,  d,^  0.9405, 

20°  15 

[ct]D  20°  28'  and  n_  1.48796. 

By  reducing  energetically  with  nascent  hydrogen 177  menthol  may 
be  obtained.  When  reduced  by  sodium  and  alcohol,  about  30  per 
cent  of  a  yellow  resin,  C20H3402,  is  formed,178  a  similar  product  being 
formed  when  employing  the  aluminum-mercury  couple.179  Paolini 
has  separated  the  alcoholic  reduction  products  (by  sodium  and  alco- 
hol) and  has  identified  ordinary  ^.menthol  of  peppermint,  a  solid 
dmenthol  melting  at  88°-89°,  boiling-point  214°,  [a]  — 11.7°,  and 
Z.pulegol. 

Pulegone  is  of  special  interest  as  furnishing  an  example  of  the 
conversion  of  the  cyclohexane  ring  into  the  cyclopentane  ring.  When 
pulegone  dibromide  is  heated  with  sodium  methylate  in  alcoholic  solu- 
tion pulegenic  acid  results,  and  when  pulegenic  acid  is  oxidized  by 
permanganate  a  glycol  is  formed  which  then  forms  a  lactone;  by  a 
pinacoline  rearrangement  the  cyclopentane  ring  is  enlarged  to  give 
C02  (loss  of  1  carbon  atom)  and  pulenone,  C9H150.180  Pulegenic 

"»J.  Proc.  Roy.  Soc.  N.  8.  W.  5k,  40  (1920). 

"•  Gildemeister,  "Die  Aetherischen  Oele,"  Ed.  2,  Vol.  I,  463. 

"'Beckmann  &  Pleissner,  Ann.  262,  30    (1891). 

178  Paolini.  J.  Chem.  Soc.  A6«.  1920  (1),  171. 

"•Harries  &  Roeder,  Ber.  32,  3357   (1899). 

"» Wallach,  Ann.  329,  82 ;  376,  154. 


THE  PARAMENTHANE  SERIES 


369 


acid  also  decomposes  with  loss  of  one  molecule  of  carbon  dioxide  to 
give  pulegene,  C9H16. 

H3 


CH3XxCH,  byKMnO< 

CH,     f  CH, 

<nto  m(J 

oxy-lacTone   '.    \  pule  none 
C-C^CH,          I 

OH        CH>  > 

CH/ 

The  ring  in  pulenone  can  be  broken  by  converting  the  oxime  into  the 
isoxime,  in  the  same  manner  as  menthone,  described  above.    Thus, 
heating  with  acetic  anhydride  gives  the  nitrile  of  a  nonylenic  acid, 
CH>  CH3  CH, 

^C.H 


pidenoneoxime    isoxime 

llWallach,  Ann.  S29,  100   (1903). 


nonylenic 
CH,    CH,     acid181 
nitrile 


370       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


Pulegene  yields  a  nitrosochloride,  melting-point  74°  to  75°,  which 
on  decomposing  with  alkali  yields  the  oxime  of  a  ketone,  pulege- 
none,182 

CH3  CH3 

CH  CH 

H,C         CH 


H2C 


H2C 


CH3 
CH 
H2C         C  =  N.OH 


!H(CH,): 


C  — Cl 
H(CH3) 


C 


pulegene 


nitrosochloride 


H(CH3)2 

oxime  of  pulegenone 


The  corresponding  saturated  ketone,   l-methyl-3-isopropylcyclopen- 
tane-2-one,  is  identical  with  camphorphorone. 

When  a  halogen,  chlorine  or  bromine,  is  introduced  into  a  ketone,  in 
the  ortho  position  to  the  carbonyl  group,  the  resulting  halogen  deriva- 
tive is  unstable.  Kotz  183  noted  that  the  bromo  ketones  are  particu- 
larly unstable,  fuming  in  the  air  and  decomposing  rapidly  when 
warmed.  Wallach  184  showed  that  the  dihalogen  ketones  react  rapidly 
with  aqueous  alkali  at  room  temperature  and  that  cyclohexanones 
could  be  converted  into  cyclopentanones  by  evaporating  the  alkaline 
solution,  thus  obtaining  an  oxy  acid  which  on  distilling  with  lead 
peroxide  and  sulfuric  acid  yields  the  pentanone, 


C=0 


182  Wallach.  Ann.  327.  133  (1903). 

™Ann.  400,  47   (1913). 

™Nachr.  Goettingen  1915,  244;  J.  Chetn.  Soc.  Alia.  110  (1),  487  (1916). 


THE  PARAMENTHANE  SERIES  371 

By  a  similar  series  of  reactions  methylcyclohexane-2-one  gives 
1  -  methycy  clopentane  -  2  -  one ;  1  -  methylcyclohexane  -  3  -  one  gives 
l-methycyclopentane-3-one;  the  ketone  1 . 3-dimethylcy  clohexane-5- 
one  yields  1 . 3-dimethylcy  clopentane-2-one ;  from  1 . 3 . 3-trimethyl- 
cyclohexane-5-one  there  was  obtained  1.3.3-trimethylcyclopentane- 
5-one. 

CH,  CH, 

CH  CH 

/\  /\ 

H2C       C  =  0  H2C         C  =  0 

H2C       CH2  H2C CH2 


Y 


H2 

CH8  CH8 

in  CH 

H2C        CH2  H2C          CH2 

H2C        C  =  0  H2C-  -C  =  0 

C 
H2 

CH3  CH3 

CH  CH 

H2C       CH2  0  =  C         CH2 

I         I      CH3  >  I  I      CH3 

0  =  C       C<  H2C C< 

\/       CH3  CH8 

•  H2 

Menthone  similarly  gives  l-methyl-3-isopropy  Icy  clopentane-2-one 
(dihydrocamphorphorone) ,  and  carvomenthone  gives  the  same 
oxidation  products.  Menthone  can  also  be  converted  into  pule- 
genone  by  slightly  modifying  the  above  procedure.  Wallach  finds 
that  menthone  dibromide  first  yields  two  isomeric  substances 
C10H1602,  one  of  which  proved  to  be  buchu  camphor. 


372      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


menthone 


buchu  camphor 


The  dibromide  of  buchu  camphor,  when  treated  with  aqueous  alkali, 
gives  an  oxy-acid  which  on  distillation  yields  pulegenone.185 

The  hydrazine  derivative  of  menthone  yields  para-menthane  when 
heated  with  caustic  potash.  Pulegohydrazine,  however,  yields  the 
bicyclic  hydrocarbon  carane,  under  these  conditions.186 


CH3 


pulegone 


carane 


This  substance,  also  called  diosphenol,  is  found  in  nature  in  the 
essential  oil  of  buchu  leaves.  It  is  of  considerable  interest  in  that 
its  chemical  behavior  gives  no  indication  of  the  existence  of  the  tau- 
tomeric  diketo  form,  analogous  to  camphor  quinone,  although  its  for- 
mation from  the  dibromine  substitution  products  of  both  menthone 
and  carvomenthone  indicate  that  the  diketone  must  be  an  intermediate 
product.187 

188Wallach,  J.  Chem.  Soc.  Als.  114,  544    (1918). 
1MKizhner.     J.  Russ.  Phys.-Cliem.  Soc.,  JtS)  1132    (1911). 

'"Cusmano,  J.  Chem.  Soc.  Ala.  191^  (1),  303;  Atti  accad.  Lincei  (5),  H,  520 
(1915). 


CH3 

CH  CH 

H2C        CHBr  H2C        CH.OH 

Hf~\  fl    ___    f\  TT/^1  f*\    /"\ 

2W  V^    \J  ±1\J  V>/    \J 

Y-B,  Y 

C3H7  C3H7 


THE  PARAMENTHANE  SERIES 
CH3 
C] 


373 


H2C 


H2C 


CH3 

C— Br 
/\ 


CH3 

C 
/\ 


\H2C 


CH 

in 

/\ 


CH3 
C 
C  =  OH,C        C  — OH 


^H,C        C  =  0  H2C        C  =  0 


^ 


C  =  0   HC        C  =  0 
CHBr   H2C        CH.OH 

\x 

CH  CH 


C3HT 


HO    TT 
,     7  ^a11? 

Carvone,  A6-8<9>-p-menthadiene-2-one.  The  constitution  of  car- 
vone and  much  of  the  chemical  behavior  has  been  shown  above,  in 
connection  with  the  discussion  of  limonene  and  the  terpineols.  Car- 
vone is  of  further  interest,  however,  on  account  of  its  conversion  to  the 
cylcoheptane  derivative  eucarvone,  and  derivatives  of  the  bicyclic 
carane  series.  Baeyer188  showed  that  the  hydrobromide  of  carvone 
gave,  by  loss  of  HBr,  an  isomeric  ketone  which  he  called  eucarvone. 
Baeyer  originally  suggested  that  the  constitution  of  eucarvone  was 
that  represented  as  I,  below,  but  Wallach  was  able  to  show  that 
eucarvone  is  a  cycloheptane  derivative  II,  and  that  Baeyer's  structure 
for  eucarvone  is  in  fact  possessed  by  an  intermediate  product  in  the 
reaction.  Wallach 189  represents  these  reactions  as  follows, 


CH3 


eucarvone 


374       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

Baeyer  regarded  dihydro  and  tetrahydroeucarvone  as  cycloheptane 
derivatives  and  showed  that  the  completely  reduced  tetrahydroeucar- 
vone was  broken  up  by  oxidation  to  (3,  p-dimethylpimelic  acid  which 
in  turn  yields  1 . l-dimethylhexane-3-one,  in  the  usual  manner: 

CH, 


cio 


H2C        C  =  0  H2C          C02H  C02H 

H2C        CH2  — *  H2C          CH2  -»  H2C          C02H. 

H2C C(CH3)2  H2C--C(CH3)2  H2C         CH2 

H2C C(CH3)2 

tetrahydro-eucarvone, 

(1 . 4 . 4-tri-methylcycloheptane-2-one,)  I 

H2C C  =  0 

H2C        CH2 

H2C--C(CH3)3 

dimethylcyclohexanone 


Eucarvone  boils  at  85°-87°  (12mm.);  its  density  at  21°  is  0.949 

20° 
and  n  — —  1.5048.    It  yields  a  semicarbazone  melting  at  183°-185° 

and  a  benzylidene  derivative  melting  at  112°-113°.  The  oxime  melt- 
ing-point, 106°,  may  be  reduced  by  sodium  and  alcohol  to  dihydro- 
eucarvylamine  and,  by  more  energetic  reduction,  to  the  saturated 
amine  C10H19.NH2.  Reduction  of  the  oxime  by  hydrogen  and  pal- 
ladium yields  the  dihydro  and  tetrahydrooximes,  melting  at  122°-123° 
and  56°-57°  respectively.  The  alcohol,  tetrahydroeucarveol  [1.4.4- 
trimethylcycloheptanol(2)],  a  product  of  reduction  by  sodium,  boils 
at  216°. 

When  carvone  is  reduced  by  nascent  hydrogen  the  double  bond 
next  to  the  CO  group  is  first  reduced,  dihydrocarvone  being  A8<9>-p- 
menthene-2-one.  Wallach,  Albright  and  Klein190  have  made  the 
interesting  observation  that  when  the  CO  group  is  converted  to  the 

™Ann.  tfS,  74   (1914). 


THE  PARAMENTHANE  SERIES  375 

oxime  and  the  resulting  carvoxime  then  reduced  by  one  mole  of 
hydrogen,  in  the  presence  of  PaaFs  colloidal  palladium,  the  double 
bond  in  the  side  chain  is  first  reduced.  In  this  case  the  oxime  of 
carvotanacetone  (A6-p-menthene-2-one)  is  formed.  Vavon 191  also 
showed  that,  in  the  presence  of  platinum  black  (Willstatter's  method) , 
carvone  itself  was  reduced  first  to  carvotanacetone.  This  ketone  is 
also  formed  by  the  rupture  of  the  three  carbon  ring  in  thujone,  effected 
by  heating.192 

Carvone  boils  at  230°  and  occurs  in  d.  and  I.  forms  [a]      ±  60° 

D 

Carvone,  dihydrocarveol  and  limonene  are  the  principal  constituents 
of  oil  of  caraway,  used  in  making  the  liqueur  "kiimmel";  carvone  is 
also  an  important  constituent  of  dill  and  spearmint  oils.  Like  citral 
and  other  substances  containing  the  group  —  CH  =  CH  —  CO  — 
carvone  reacts. to  form  an  unstable  bisulfite  compound  from  which 
carvone  can  be  regenerated  by  alkali,  and  also  forms  stable  salts  of 
the  dihydrosulfonic  acid  derivative,  from  which  the  ketone  cannot  be 
regenerated.  Carvone  forms  a  crystalline  compound  with  hydrogen 
sulfide,  (C10H140)2.H2S,  from  which  carvone  can  be  regenerated.193 
The  bisulfite  method  is  preferable  for  the  isolation  of  carvone.  For 
its  identification,  the  following  derivatives  are  characteristic:  the  d. 
and  Z.oxime,  melting-point  72°,  i-carvoxime  melting-point  93°  (when 
too  great  an  excess  of  hydroxyamine  is  employed  a  compound  of  car- 
voxime  and  hydroxylamine,  C10H14NOH.NH2OH.,  melting  at  174°- 
175°,  is  formed.  It  will  be  of  interest  to  note  that  in  the  preparation 
of  carvoxime  a  Walden  inversion  occurs,  d.  carvone  yielding  Z.carvox- 
ime  and  i.carvone  yielding  dcarvoxime.  With  phenylhydrazine  car- 
vone  forms  a  phenylhydrazone  melting  at  109°-110°  and  semicarbazid 
forms  a  semicarbazone  melting  at  162°-163°  in  the  case  of  d.  or 
{.carvone  but  i-carvone  yields  the  racemic  semicarbazone  melting  at 
154°-156°.  Jfhe  original  ketones  are  readily  regenerated  by  warm- 
ing the  semicarbazones  with  oxalic  acid. 

Carvoxime  rearranges  to  amido  thymol  when  treated  with  con- 
centrated sulfuric  acid, 

»lCompt.  rend.  153,  68    (1911). 

192  Semmler,  Ber.  27,  895    (1894). 

193  Wallach,  Ann.  SOS,  224    (1889)  ;  Claus  &  Fahrion,  J.  prakt.   CJiem.   (2),  S9,  365 
(1889).     The  product  from  d.  or  1.  carvone  melts  at  210°-211°  ;   that  from  i.  carvone 
melts  at  189°-190°.     It  is  dimolecular  in  benzene  but  monomolecular  in  glacial  acetic 
acid.     Deussen,  Arch.  Pharm.  221,  285  (1883). 


376       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


HC 
H2 


CH3 
C 


CH3 
C 
HC        C  =  N.OH 


CH, 


C       CH2  HC 


CH, 


YH 
i 


V 


CH3        CH2 


CH 
CH,        CH, 


HC        C  — NH2 
HOC        CH 

Y     ' 

AH 

CH3        CH3 

amidothymol 


By  the  Grignard  reaction,  using  methyl-magnesium  iodide,  a  hy- 
drocarbon, CnH16,  results.194  Klages  regards  this  hydrocarbon  as 
2-methyl-A2t6-8(9)-menthatriene  on  account  of  the  ease  with  which  it 
is  isomerized  to  2-methylcymene  by  boiling  with  a  2  per  cent  solu- 
tion of  hydrogen  chloride  in  acetic  acid.195  The  reaction  is  worth 
noting  as  one  of  the  many  instances  of  the  migration  of  a  double  bond 
from  a  side  chain  to  the  cyclohexadiene  nucleus  to  give  a  benzene 
derivative. 


carvone          2-methylcarveol 


2-methylcymene 


When  dihydrocarvone  is  similarly  treated,  2-methyldihydrocarveol 
results  which  can  be  decomposed  directly,  or  better  by  converting  to 
the  corresponding  chloride,  to  2-methylhomolimonene,  or  hydrated 
by  the  action  of  alcoholic  sulfuric  acid  to  2,8-dihydroxy-2-methyl- 
menthane.196  The  main  product  of  the  action  of  magnesium-benzyl- 

184Rupe  &  Liechtenhan,  Ber.  39,  1119   (1906). 

198  Ber.  39,  2306   (1906)  ;  Rupe  &  Emmerich,  Ber.  41,  1393   (1908). 

189  Rupe  &  Emmerich,  loc.  cit. 


THE  PARAMENTHANE  SERIES 


377 


chloride  is  a  ketone,  6-benzyl-A8-p-menthene-2-one,  [or  6-benzyldi- 
hydrocarvone] ,  melting  at  73°.  The  a-naphthyldihydrocarvone, 
melting-point  150°,  was  prepared  in  the  same  manner.197 

Semmler 198  has  employed  the  reaction  of  carvone  with  magnesium- 
isoamylbromide  for  the  synthesis  of  a  hydrocarbon  of  the  sesquiter- 
pene  class.  (When  ether  is  used  as  a  solvent  in  the  Grignard  reac- 
tion, instead  of  benzene,  a  large  proportion  of  isoamyldihydrocarvone 
is  formed.)  The  synthetic  sesquiterpene  thus  prepared  is  monocyclic, 
contains  three  double  bonds  and  has  been  named  isoamyl-a-dehydro- 
phellandrene  by  Semmler. 

Carvone  is  isomerized  by  sunlight  forming  a  resin  and  a  crystal- 
line camphor-like  substance,  melting  at  100°,  which  Ciamician  and 
Silber  named  carvone-camphor.199  This  substance  has  been  carefully 
investigated  by  Sernagiotto,200  who  showed  that,  in  sealed  tubes,  the 
sunlight  causes  both  double  bonds  in  carvone  to  combine  to  form  a 
four-carbon  ring.  Ciamician  had  suggested  that  the  isomerization  of 
carvone  resembled  that  of  the  condensation  of  two  molecules  of  cin- 
namic  acid  to  form  truxillic  acid.  The  work  of  Sernagiotto  shows 
that  the  chemical  behavior  of  the  substance  may  be  indicated  as 
follows, 

CH2 CH CH2 


—  CH, 
H, 


CH9 CH 


carvone 
-CH2 


—  CH3 

/L 


CH 


CH2 — C  =  O 
C  — CH3 
CH2 

A: 


CH- 


C02H 


carvone-camphor 


CH3 

ketonic  acid 


lwRupe  &  Tomi,  Ber.  47,  3064  (1914)  :  ZelinskI,  German  Pat.  202,720  (1909). 

™Ber.  50,  1838   (1917). 

399  Ber.  11,  1928   (1908). 

*»>Atti  accad.  Lincei  23   (2),  70   (1914)  ;  26;  238   (1917). 


378      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


Carvone  camphor  melts  at  100°,  boils  at  205.5°,  forms  an  oxime  melt- 
ing at  126°-128°  and  a  semicarbazone  melting  at  239°. 

Like  menthone,  pulegone  and  camphor,  carvone  can  be  condensed 
with  aniline  by  heating  with  aniline  in  the  presence  of  a  little  zinc 
chloride  [or  ZnCl2.  (C6H5NH2)2].  The  resulting  carvoneanil  is 
an  oil.201 

It  is  pointed  out  by  Lapworth  202  that  when  the  double  bond  in  the 
ring  of  carvone  combines  with  hydrogen  cyanide,  the  resulting 
CHa  CH, 


H 


NC 
H 


\C 
/*\ 


HCN 


YH 


H2 


H 


oV^  V_/XJ-o 

'  \*/ 

CH 


CH 


/\ 


CH, 


CH3        CH2 


cyanodihydrocarvone  should  theoretically  be  capable  of  existence  in 
four  stereoisomeric  forms  having  three  asymmetric  carbons,  as  shown. 
By  employing  Aschan's  scheme  of  representing  the  section  of  the 
ring  plane  by  a  line,  these  four  isomerides  can  be  represented  as  fol- 

CH3 

lows,  Pr  representing  the  group  —  C 

\H2  I 

Pr  Pr  Pr  Pr 


CN 
CH3 


GEL 


CN 


CN 
CH3 


CN 


CH3 


(1)  (2)  (3)  (4) 

The  ordinary  form,  melting-point  93.5°-94.5°,  is  obtained  in  excellent 
yields  when  an  alcoholic  solution  of  carvone  and  potassium  cyanide 
is  treated  with  acetic  acid  in  amounts  which  insure  the  presence  of  a 


201  Reddelien  &  Meyn,  Ber.  53,  B    345   (1920) 

202  J.  Chem.  Soc.  89,  946   (1906). 


THE  PARAMENTHANE  SERIES  379 

little  excess  potassium  cyanide.  When  the  addition  of  hydrogen 
cyanide  takes  place  in  hot  solutions  a  different  crystalline  isomeride 
is  produced  in  considerable  quantity  which  has  a  rotatory  power  in 
the  opposite  sense  to  that  of  the  substance  described  above  [a],-.  — 39°, 

instead  of  [«]pv  +  15.4°.    The  Z.isomeride  exhibits  slight  mutarota- 

tion  and  Lapworth  considers  that  the  four  isomerides  may  be  divided 
into  two  pairs,  the  two  members  of  each  pair  being  dynamic  isomer- 
ides at  ordinary  temperatures.203 

Perillic  aldehyde,  occurring  in  the  essential  oil  of  PerUla  nan- 

kinensis,  has  been  found  to  contain  two  double  bonds  in  the  A6-8<9> 

positions,  as  in  limonene.    By  reduction  with  zinc  dust  and  acetic 

!  acid  an  alcohol  is  produced  which  is  identical  with  the  so-called  dihy- 

:  drocuminic  alcohol  previously  found  in  gingergrass  oil.    Its  constitu- 

!  tion  was  shown  by  converting  the  CH2OH  group  of  perillic  alcohol 

j  to  the  chloride  which  on  reducing  by  sodium  and  alcohol  gave  Uimo- 

;  nene.    On  dehydrating  the  oxime  of  perillic  aldehyde  the  correspond- 

i  ing  nitrile  is  formed  which  on  hydrolysis  yields  perillic  acid.    Reduc- 

!  tion  of  the  ester  of  perillic  acid  with  sodium  in  absolute  alcohol 

reduced  one  of  the  double  bonds  and  gave  dihydroperillic  alcohol.204 

CHO  CH2OH  C02H  CH2OH 

k  A  A        H-A 

HC        CH2          HC        CH2          HC        CH2        H2C        CH, 


[2C        CH2        H2C        CH2        H2C        CH2        H2C        CH2 
CH  CH  CH  CH 

A  A  A  A 


CH3        CH2 

perillic 
aldehyde  265 

CH3        CH2 

perillic 
alcohol 

CH3        CH2 

perillic 
acid 

CH3        CH2 

dihydroperillic 
alcohol 

203  Lapworth  &  Steel,  J.  Chem.  Soc.  99,  1877  (1911). 

2<*Semmler  &  Zaar,  Ber.  44,  52   (1911). 

zee  The  physical  properties  of  these  substances  are  as  follows : 

Perillic                  Perillic  Perillic               Perillic 

aldehyde                  alcohol  nitrile                  acid 

Boiling-point    (10mm.)    ..      104°-105°      119°-121°  (llmm.)  116°  (llmm)            164« 

Density     0.9617(18°)          0.9640(20°)  0.9439                

[a]    D    —146°                   —68.5°  —115°            — 20°  (25% 

"D     1.5074                    1.4996  1.4977                a^h.ol) 

Perillic  acid  melts  at  130°-131°. 


CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


The  Phellandrenes. 


As  early  as  1842,  Cahours  noted  a  terpene  boiling  at  173°-175° 
in  the  essential  oil  of  bitter  fennel,  which  gave  a  crystalline  nitrosite. 
The  correct  empirical  formula  of  this  nitrosite,  C10H16N203,  was  first 
established  by  Pesci,206  who  showed  that  "phellandrene"  from  the 
essential  oil  of  water  fennel,  Phellandrium  acquaticum,  also  yielded  a 
nitrosite  of  the  same  empirical  formula.  Both  phellandrenes  were 
dextro-rotatory  and  yielded  laevo  nitrosites  of  nearly  identical  physi- 
cal properties;  the  phellandrenes  from  both  sources  were  unstable  and 
even  by  repeated  distillation  were  converted  to  limonene.  Wallach 
took  up  the  study  of  the  phellandrenes  in  1902  and  a  little  later  207 
showed  that  d.phellandrene  from  elemi  oil  and  d.phellandrene  from 
bitter  fennel  oil  were  identical  in  every  respect  and  that  Z.phellandrene 
from  Eucalyptus  amygdalina  oil  was  the  corresponding  laevo  form; 
that  the  dphellandrene  from  water  fennel  oil  is  a  different  hydro- 
carbon, and  therefore  designated  the  two  hydrocarbons  as  a-phellan- 
drene  and  (3-phellandrene,  respectively. 

That  a-phellandrene  belonged  to  the  paramenthane  series  of  hydro- 
carbons was  early  recognized  by  reason  of  the  easy  conversion  of  the 
dibromide  to  cymene.208 

The  constitution  209  of  a-phellandrene  is  indicated  by  its  conversion 
to  carvotanacetone  (A6-p-menthene-2-one)  .  When  a-phellandrene 
nitrite  is  heated  with  alcoholic  caustic  potash,  nitro-a-phellandrene  is 
formed  which,  on  careful  reduction  by  zinc  and  acetic  acid,  yields 
carvotanacetone,  the  constitution  of  which  had  previously  been  estab- 
lished, 


a-phellandrene 


a-phellandrene 
nitrite 


**Gazz.  chim.  Ital.  16,  225   (1886). 

207  Ann.  336,  9   (1904). 

208  Ann.  287,  383. 

209  Wallach,  loc.  cit. 


nitro-cn- 
phellandrene 


carvo- 
tanacetone 


THE  PARAMENTHANE  SERIES  381 

The  constitution  of  ct-phellandrene  shown  above  is  confirmed  by  its 
synthesis  from  4-isopropyl-A2-cyclohexenone.210 


0  CH3  CH3 

&  A-OH  i 

H2C        CH  H,C 


MgCH.l 


H2C        CH  H2C        CH 


N/L  \/  V 

r*Tj                                  OTI  r^tr 

v^xl                                          \jJUL  v^H 

C3HT                         C3H7  C3H 


In  carrying  out  the  above  synthesis  the  intermediate  alcohol  is  not 
liberated  as  such  but  the  magnesium-methyl  halide  addition  product 
decomposes  in  the  reaction  mixture  to  give  the  hydrocarbon.  Hydro- 
carbon formation  is  often  observed  under  these  conditions. 

a-Phellandrene  nitrite  is  known  in  two  forms.  It  is  best  pre- 
pared 211  in  ligroin  solution,  shaking  the  ligroin-phellandrene  mixture 
with  concentrated  aqueous  sodium  nitrite  acidified  by  acetic  acid. 
The  two  nitrites  may  be  separated  by  crystallization  from  dilute 
acetone.  The  sparingly  soluble  a-nitrite,  melts  at  112°-113°, 
[a]D+136°  to  143°,  [a]D  —  138°.  The  p-nitrite  is  more  soluble 

and  melts  at  105°    [a]     +  45.8°   and   [a]     —40.8°.    On  reduction 

these  nitrites  give  a  diamine,  the  hydrochloride  of  which  decomposes 
on  distillation  yielding  cymene. 

(3-Phellandrene  also  yields  two  known  nitrites,  the  so-called 
a-nitrite  melting  at  102°  and  the  p-nitrite  melting  at  97°-98°.  When 
p-phellandrene  nitrite  is  converted  to  nitro-p-phellandrene  and  when 
this  is  reduced  by  sodium  and  alcohol,  dihydrocumin  aldehyde  is  pro- 
duced,212 indicating  that  its  structure  is  either 

310  Wallach,  Ann.  S59,  285. 

211  Wallach,  Ann.  313,  345  ;  S36,  13. 

212  Wallach,  Ann.  340,  9. 


382       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


H2C 


r 

/\ 


CH 


or 


H 


H 


H2C        CH 

YH 

C3H7  C3H7 

However,  p-phellandrene  is  optically  active  which  eliminates  II,  which 
has  no  asymmetric  carbon  atom.  The  decomposition  of  nitro  deriva- 
tives with  the  formation  of  aldehydes  has  been  observed  by  Kono- 
walow213  and  others.  Careful  oxidation  of  p-phellandrene  by  per- 
manganate yields  first  a  glycol  which  on  decomposing  with  acids, 
yields  tetrahydrocuminaldehyde, 

H.OH  -         CHOH    _  CHO 


p-phellandrene  glycol  tetrahydro- 

cuminaldehyde 

Isopropylcyclohexenone  is  formed  by  air  oxidation  of  p-phellandrene 
in  the  presence  of  moisture,214  which  may  be  expressed,  according  to 
Engler's  theory  of  air  oxidation,  as  follows, 


»"  Ohem.  Zentr.  1889,  I,  1238. 
w«Wallach,  Ann.  Stf,  29  (1905). 


THE  PARAMENTHANE  SERIES  383 

The  following  physical  properties  of  the  phellandrenes  have  been 
noted: 

l.a-phellandrene,  boiling-point  65°  (12mm.),  d^  0.8465,  nD  1.488. 

d.a-phellandrene,    boiling-point    61°  (llmm.),    d          0.844,    n.^ 

1.4732. 

Synthetic   a-phellandrene,    boiling-point    175°-176°    d          0.841, 

D      1.4760,  MD  45.61. 

20° 

dfi-phellandrene,   boiling-point   57° (llmm.),    d2QO    0.8520,   n-^- 

1.4788,  [a]D  + 18.54  (?). 

The  essential  oil  of  Bupleurum  fruticosum  yields  d(3-phellandrene 
showing  an  optical  rotation  of  [a]  _^  65.2°,  from  which  fact,  together 

with  evidence  obtained  by  a  study  of  the  oxidation  products  and  the 
nitrosochlorides,  the  discoverers 215  conclude  that  the  d.(3-phellandrene 
of  Pesci  and  Wallach,  which  showed  a  much  lower  rotatory  value, 
is  a  mixture  of  the  two  optical  antipodes.  A  terpene  fraction  boiling 
at  169°-171°,  isolated 216  from  the  volatile  oil  of  Rubieva  multifida  of 
California,  and  consisting  "largely"  of  (3-phellandrene,  showed 
[a]D+46.4°. 

Hydrogen  chloride  passed  into  an  alcoholic  solution  of  (3-phellan- 
drene  gives  a-terpinene  dihydrochloride.217 

218  Fransesconi  &  Sernagiotto,  Gazz.  chim.  Ital.  46  (1),  119   (1916). 

"•Nelson,  J.  Am.  Chem.  Soc.  42,  1286  (1920). 

217  Fransesconi  &  Sernagiotto,  Gazz.  chim.  Ital.  44   (2),  456   (1914). 


Chapter  X.     Cyclic  Non-benzenoid 
Hydrocarbons. 

Ortho-  and  Meta-Menthanes  and  Their  Derivatives. 

Sylvestrene:  The  most  important  derivative  of  this  series  is  syl- 
vestrene, a  terpene  discovered  by  Atterberg  in  Swedish  oil  of  turpen- 
tine, from  Pinus  sylvestris.  Its  physical  properties  are  nearly  identi- 
cal with  those  of  limonene,  boiling  at  175°-176°.  It  is  one  of  the 
most  stable  of  the  terpenes  and  is  not  isomerized  to  other  terpene 
hydrocarbons  either  by  the  action  of  heat  or  dilute  acids.  Its  rela- 
tion to  meta-cymene  was  shown  by  Baeyer  by  first  reacting  upon  it 
by  hydrogen  bromide  forming  the  dihydrobromide  (melting-point 
72°),  introducing  a  third  bromine  atom  and  treating  the  tribromide 
with  zinc  dust  and  alcoholic  hydrochloric  acid  when  meta-cymene  was 
produced.  Under  these  same  condition  limonene  gives  para-cymene. 
The  inactive  form  of  this  terpene  has  been  called  carvestrene  and 
bears  the  same  relation  to  sylvestrene  that  dipentene  bears  to  limo- 
nene. Baeyer1  made  i-sylvestrene  from  carvone  by  reducing  this 
ketone  by  sodium  and  alcohol  to  dihydrocarveol,  oxidizing  this  alcohol 
to  dihydrocarvone  and  adding  hydrogen  bromide  to  the  latter  ketone; 
when  the  hydrobromide  of  dihydrocarvone  is  treated  with  cold  alco- 
holic caustic  potash,  carone  is  formed,  which  substance  has  been 
shown  to  have  a  cyclopropane  ring.  The  oxime  of  carone  is  reduced 
in  the  usual  manner  to  the  corresponding  amine,  and  warming  witfc 
dilute  acids  ruptures  the  three-carbon  ring.  When  the  hydrochloride 
of  this  amine  is  heated,  ammonium  chloride  is  split  off  and  i-sylves- 
trene (carvestrene)  is  produced. 

lBer.  27,  3485. 

384 


ORTHO  AND  METAMENTHANES 


385 


carvone        dihydrocarveol  dihydrocarvone 


carone 


vestrylamine       i-sylvestrene 


The  nature  of  the  reaction  taking  place  when  the  hydrobromide 
of  dihydrocarvone  is  treated  with  alkali  to  form  carone,  and  the  con- 
stitution of  carone,  was  first  suggested  by  Wagner,  whose  views  were 
accepted  by  Baeyer.  In  conjunction  with  Ipatiev,  Baeyer  investi- 
gated the  oxidation  of  carone  by  permanganate2  and  showed  the 
formation  of  two  isomeric  dibasic  acids,  C5H8(C02H)2,  one  of  which 
readily  forms  an  anhydride  (when  boiled  with  acetyl  chloride)  but 
the  other  does  not  form  an  anhydride  under  these  conditions.  Their 
research  led  Baeyer  and  Ipatiev  to  the  conclusion  that  these  two 
caronic  acids  were  cis  and  trans  modifications  of  the  following  struc- 
ture, 

C(CH3)2  C(CH3)2 

C C  — C02H  H  — C C  — H 


H02C 


trans-caronic  acid 

*Ber.  29,  2796    (1896). 


C02H  C02H 
cis-caronic  acid 


386       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

The  correctness  of  the  constitutions  shown  above  was  proven  by 
W.  H.  Perkin,  Jr.,  and  J.  F.  Thorpe,3  who  synthesized  the  caronic 
acids  from  bromodimethylglutaric  ester, 


C(CH3)2 
C2H502C  -  CHBr        H.CH.C02C2H{ 


R02C  -  CH 


C(CH3)2 
-  CH.C02R 


Trans-caronic  acid  is  converted  to  the  anhydride  of  cis-caronic  acid 
by  heating  with  acetic  anhydride  at  220°. 

Inactive  sylvestrene  has  been  synthesized  by  Perkin 4  by  means  of 
the  Grignard  reaction.  Starting  with  meta-hydroxybenzoic  acid, 
which  was  reduced  to  cyclohexanol-3-carboxylic  acid  and  this  oxi- 
dized to  the  corresponding  ketone,  the  reactions  may  be  represented 
as  follows,  being  parallel  to  the  reactions  employed  by  Perkin  for  the 
synthesis  of  limonene. 


It  is  evident  that  Baeyer's  i-sylvestrene  can  be  only  the  A1  hydro- 
carbon, but  Perkin's  synthetic  hydroc'arbon  may,  from  the  method  of 
its  preparation,  be  either  A1  or  A6  hydrocarbon,  although  Perkin's 
results  indicate  that  his  synthetic  sylvestrene  consists  at  least  mainly 
of  the  A1  product. 

*J.  Chem.  Boc.  75,  49   (1899). 


OR THO  AND  METAMENTHANES 


387 


Sylvestrene  cannot  be  isolated  from  Swedish  oil  of  turpentine  by 
fractional  distillation  on  account  of  the  presence  of  other  terpenes  of 
practically  the  same  boiling  point.  It  has  usually  been  prepared  by 
making  the  crystalline  dihydrochloride  from  the  fraction  boiling  at 
173°-178°  and  decomposing  this  with  an  alkali  or  an  organic  base. 
Wallach  observed  that  the  terpene  so  prepared  was  not  pure  but  by 
fractional  distillation  of  the  product  obtained  by  decomposition  of  the 
dihydrochloride  obtained  a  sylvestrene  of  the  following  physical  prop- 
erties. 


Blg.-pt.  175°-176°;  d 


0.848;  n      1.4757;  [a]      +66.32. 
20°  D  D 


It  is  well  known  that  the  decomposition  of  dipentene  dihydro- 
chloride or  ordinary  terpin,  and  also  terpinene  dihydrochloride  or 
terpinene-terpin  (1.4  terpin)  yields  mixtures  of  terpenes  and  it  would 
therefore  appear  probable  that  the  decomposition  of  sylvestrene  dihy- 
drochloride would  also  yield  a  mixture  of  hydrocarbons.  The  first 
definite  demonstration  that  sylvestrene  dihydrochloride  is  1.8-di- 
chloro-m.-menthane  was  the  conversion  of  dl.-m.-hl-menthenol(8)  and 
d/.-ra.-A6-menthenol(8)  into  this  dihydrochloride,5 


A-m-menThenol(8)  CH3 


dih_ydrochloride 


The  decomposition  of  this  dihydrochloride  could  possibly  yield  the 
following  six  isomeric  meta-menthadienes. 

*  Perkin  &  Tattersall,  J.  Chem.  Soc.  91,  481  (1907)  ;  Perkin  &  Fisher,  ibid.,  93,  1888 


388 


CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 
CHa  CH3  CH2 


i 


HC        CH. 

(1) 


V 

H2 
CH8 
C 
HC       CHS 


CH3 


GIL 


\ 


CHa 


CH« 


/ 
\ 


CH3 


The  hydrocarbons  represented  by  (4),  (5),  and  (6)  have  no  asym- 
metric carbon  atom  and  since  sylvestrene  is  optically  active  its  struc- 
ture cannot  be  (4),  (5)  or  (6).  Also,  sylvestrene  does  not  show  the 
chemical  behavior  of  a  substance  having  a  semicyclic  >C  =  CH2 
group,  which  renders  the  structure  (3)  very  improbable.  Haworth, 
Perkin  and  Wallach  6  have  shown  that  repeated  fractionation  of  the 
crude  sylvestrene,  made  by  heating  the  dihydrochloride  with 
diethylaniline,  yields  a  sylvestrene  boiling  at  175°  (751mm.)  and 
[a]-~  +  83.18°  at  18°.  A  higher  boiling  fraction  was  also  isolated, 

boiling   at   182°-184°    and    [a]     +  45.42°.    This   terpene   resinifies 

rapidly  on  exposure  to  air,  or  in  contact  with  sodium,  and  the  authors 
conclude  that  it  contains  a  considerable  proportion  of  inactive  syl- 
veterpinolene  together  with  some  isomeride  of  similar  boiling-point 
but  optically  active.  The  purest  sylvestrene  thus  obtained,  boiling 
at  175°,  is  regarded  as  a  mixture  of  the  A1  and  A6  isomerides,  (1)  and 
(2)  above.  All  efforts  to  obtain  a  pure  sylvestrene  of  definite  con- 

•J.  Chem.  Soc.  103,  1230  (1913). 


ORTHO  AND  METAMENTHANES 


389 


stitution  by  the  dehydration  of  sylveterpin,  under  different  conditions, 
were  without  success  owing  to  the  marked  tendency  of  the  sylveterpin 
to  form  meta-cineol, 


The  complexity  of  the  problem  is  indicated  in  the  foregoing  discus- 
sion but,  nevertheless,  Haworth  and  Perkin7  were  able  to  synthesize 
both  optically  active  forms  of  sylvestrene  and  their  research,  cul- 
minating with  the  synthesis  of  d.  and  £. sylvestrene,  is  one  of  the  most 
interesting  examples  of  refined  experimental  method  and  application 
of  the  theories  of  organic  chemistry. 

The  removal  of  hydrogen  bromide  from  1-bromo-l-methylcyclo- 
hexane-3-carboxylic  acid  yields  a  mixture  of  the  A1  and  A6  unsaturated 
acids. 


By  fractional  crystallization  of  the  brucine  salt  an  optically  active 
acid  [a]^  +  108°  was  isolated,  and  from  the  mother  liquors,  by  em- 
ploying Z.menthylamine,  another  acid  [a]^  —  49.7°  was  obtained. 

In  order  to  show  which  of  these  acids  was  the  A1  and  which  the  A6 
acid,  the  latter  was  synthesized  from  l-methylcyclohexane-6-one-3- 
carboxylic  acid, 

»«/.  Chem.  Soc.  MS,  2229   (1913). 


390       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


-COZH 


and  this,  on  resolution  by  brucine,  also  gave  an  acid  [a]     +108° 
and  the  laevo  form  [a]^  —  98.6°.    This  dextro-rotatory  acid,  from 

both  sources,  was  converted  into  d-A6-m-menthenol(8),  which  in  turn 
was  changed  to  d.-sylvestrene  dihydrochloride,  [«]-pv  +  22.5°,  which 

on  decomposition  by  diethylaniline  gave  d-sylvestrene,  [a] 


The  Isevo  A6  acid,  [a]D  —  98.6°,  and  the  laevo  A1  acid,  [a]D  —  49.7° 

both  gave  l-sylvestrene,  by  similar  reactions,  the  rotation  being 
—  66.5°  in  one  case  and  —  68.2°  in  the  other. 

Sylveterpin  and  Sylveterpineols:  When  sylvestrene  dihydrochlo- 
ride is  shaken  with  dilute  aqueous  caustic  potash  the  corresponding 
terpin  is  formed.  Like  ordinary  terpin,  sylveterpin  exists  in  two 
modifications  of  the  cis  and  trans  type,  the  cis  form  melting  at 
137°-138°,  being  less  soluble,  was  discovered  first,8  and  the  more  solu- 
ble trans  form,  melting  at  70°-75°,  was  recently  discovered9  in  the 
mother  liquors  after  separating  the  first  or  cis  form.  The  cis  and 
trans  forms  of  sylveterpin  are  the  d.  constituents  of  the  inactive  or 
cis  and  trans  carveterpins.  TVans-carveterpin,  melting  at  126°-127°, 
was  discovered  by  Baeyer  during  his  researches  on  i-sylvestrene  (or 
"carvestrene").10 

Sylveterpineol,  the  chief  product  of  the  action  of  dilute  alkali  on 
sylvestrene  dihydrochloride,  has  been  shown,11  by  study  of  its  oxida- 
tion products  to  be  a  mixture  of  A6-m-menthenol  (8)  and  A^m-men- 
thenol(8).  The  mixture  distills  at  214°.  The  menthenols  obtained 
by  synthesis,  employing  the  Grignard  reaction  as  described  in  the 
foregoing  pages,  are  usually  obtained  quite  pure.  All  of  the  six 
theoretically  possible  raeta-menthenols,  having  the  hydroxyl  group 
in  position  (8)  are  known.12  When  these  meta-menthenols  are  decom- 

8  Wallach,  Ann.  357,  73   (1907). 

•Haworth,  Perkin  &  Wallach,  J.  Chem.  Soc.  103,  1234    (1913). 

™Ber.  27,  3490  (1894). 

11  Haworth,  Perkin  &  Wallach,   loc.  cit. 

"Perkin,  J.  Ohem.  Soc.  07,  2129  (1910). 


ORTHO  AND  METAMENTHANES 


391 


posed  a  mixture  of  hydrocarbons  results  except  in  the  case  of  A2  or 
A3-m-menthenol(8);  which  can  decompose  with  loss  of  water  only  in 
one  way. 

CH3 
CH 
H2C        CH2 


CH, 


H, 


—  C 


C  OH  CH3 


&3-m-menthenol(8) 


CH3 
—  C 

Y     V 
u±i2 

H 

t9)  -m-menthadiene 


This  hydrocarbon  is  of  interest  as  showing  the  effect  of  the  conjugation 
of  the  two  double  bonds  upon  the  physical  properties,  as  compared 
with  the  isomeric  m6£a-menthadienes.13  Its  physical  properties  closely 
resemble  the  similarly  constituted  A3  8<9>-p-menthadiene. 

I.    A2  8<9>—  m-menthadiene  14 
A3:8(9)  —  m-menthadiene 
A3  8<9>—  p-menthadiene 


II. 
III. 


IV.    A1  8(9)  —  p-menthadiene  (limonene). 

/.  //. 

Boiling-point    .......      182°  181°-182° 

20° 

d-  ...............  0-8624  0.8609 


184°-185° 
0.8580 

1.4924 
46.02 


IV. 
175°-176° 

0.8460 

1.4746 
45.23 


nD    1.5030  1.4975 

M    46.6  46.3 

M.  calc.  for  C10H16/=2    45.24. 

Dihydrosylveterpineol  [m-menthanol(8)]  possesses  two  asym- 
metric carbon  atoms  and  accordingly  exists  in  two  slightly  different 
isomeric  forms,  the  activity  of  one  being  due  to  the  carbon  atom  (1), 
and  in  the  isomer  carbon  atom  (3)  is  active.  The  latter  substance 
is  obtained  by  the  catalytic  hydrogenation  of  sylveterpineol  and  the 
former  is  prepared  by  synthesis  from  l-methyl-3-acetylcyclohexane.15 

13  Luff  &  Perkin,  J.   Chem,  Soc.  97,  2154    (1910). 

"Haworth,  Perkin  &  Wallach,  J.  Chem.  Soc.  99,  120   (1911). 

13  Haworth,  Perkin  &  Wallach,  J.  Chem.  Soc.  103,  1228  (1913).     Wallach,  Ann.  S81, 


392       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


[a] 


form, 
10.35 


ph.  ur  ethane,  M.-P.  IT 


d(l)  form, 
[a]D+1.96° 

ph.  ur  ethane,  M.-P.  83 ( 


Ortho-Menthane  Derivatives:  Menthenols  and  menthadienes  of 
the  ortho  series  have  not  been  found  in  nature  but  we  have  a  fairly 
complete  knowledge  of  them  due  largely  to  the  systematic  researches 
of  Perkin,  Jr.,  and  his  assistants.  The  methods  of  synthesis  employed 
by  Perkin  to  obtain  the  substances  of  this  series  are  quite  closely 
analogous  to  those  already  described  in  connection  with  the  para  and 
raeta-menthane  derivatives.  Of  the  six  possible  or£/io-menthenols,  in 
which  the  hydroxyl  group  occupies  postion  (8),  five  are  known.  Their 
boiling-points  under  30mm.  pressure  are  given  for  the  known  ortho- 
menthenols, 


Of 


A5  110° 


ORTHO  AND  METAMENTHANES 


Like  the  m-menthenols,  these  of  the  ortho  series  have  odors  closely 
resembling  a  mixture  of  terpineol  and  menthol.  No  attempt  has  been 
made  to  resolve  the  synthetic  inactive  o-menthenols  into  their  active 
d  and  I  constituents.  A1-o-menthenol  (8)  was  synthesized  from  ortho 
toluic  acid,  which  will  serve  to  illustrate  a  typical  synthesis  of  this 
series.  Reduction  by  sodium  and  amyl  alcohol  gave  1-methyl-cyclo- 
hexane-2-carboxylic  acid  which  was  then  brominated  and  then  decom- 
posed to  the  unsaturated  acid  which  was  proven  to  be  1 -methyl- A1- 
cyclohexene-2-carboxylic  acid  by  oxidation  with  permanganate  to 
3-acetobutyric  acid. 


CH 


1 8/9)    ^^"^ 
A-0-menthenol(8)         A    -0-merithadiene 


/CO.H 


«. 

3- aceto butyric  acid 


As  in  the  case  of  A2-m-mentheriol  (8) ,  this  o-menthenol  can  decom- 
pose with  the  formation  of  a  double  bond  in  only  one  direction  and 
accordingly  the  resulting  A18(9)-o-menthadiene  is  quite  pure.  It  ex- 
hibits the  usual  characteristics  of  a  hydrocarbon  containing  conjugated 
double  bonds,  combines  with  only  one  molecule  of  a  halogen  or  halo- 
gen acid,  exhibits  exaltation  of  the  molecular  refraction,  has  a  boiling- 
point  higher  than  its  isomers  which  do  not  have  their  double  bonds  in 
conjugated  position,  resinifies  rapidly  in  contact  with  air  or  on  warm- 
ing with  metallic  sodium,  etc.  The  same  o-menthenol  and  o-men- 
thadiene  was  synthesized  in  quite  a  different  manner  by  condensing 
diacetylpentane  (by  means  of  sulfuric  acid)  and  treating  the  resulting 
unsaturated  ketone  with  magnesium-methyl-iodide  in  the  usual  manner. 


394       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


H9C        C  —  COCH, 


H2C        C  — C(CH3) 


For  the  preparation  of  the  A5  and  A6-o-menthenols  and  the  o-men- 
thadienes  resulting  from  their  decomposition  Perkin  was  compelled 
to  make  use  of  an  ingenious  method  of  separating  the  1-methyl-A5 
and  l-methyl-A6-cyclohexenecarboxylic  acids.  Haworth  and  Per- 
kin 16  had  observed  that  of  the  following  two  acids  the  A4  acid  esteri- 
fies  much  more  rapidly  and  the  ester  is  hydrolyzed  or  saponified  much 
more  rapidly  than  the  A5  acid. 


CH3 
CH 
HC        CH  — C02H 


HC  —  CH2 
A*  acid 


CH8 
C 
HC        CH  —  C02H 

C  — 


H 


CH, 


A5  acid 


It  was  found  that  the  methylcyclohexenecarboxylic  acids  showed  a 
parallel  behavior,  the  6-acid  esterifying  much  less  rapidly  than  the 
5-acid. 

18  J.  Chem.  8oc.  93,  577   (1908). 


ORTHO  AND  METAMENTHANES 
CH8  CH3 

CH  C 

HC       CHC02H.  HC       CHC02H. 

A6 
H2C       CH2 

C 
H2 

A5-esterifies  much  more  rapidly  than  A6.  Perkin  was  able  to  effect  a 
fractional  separation  of  these  two  acids  by  making  use  of  this  fact, 
and  then  synthesized  the  corresponding  o-menthenols  in  the  usual 
manner. 

O-Menthane-5-One:  The  first  o-menthanone  to  be  described  was 
prepared  by  reduction  of  l-methyl-2-isopropyl-A6-cyclohexene-5- 
one.17  This  o-menthone  boils  at  204°  and  yields  an  oxime  melting 
at  75°. 

"Kotz  and  Anger,  Ber.  44,  466  (1911). 


Chapter  XL     Cyclic  Non-benzenoid 
Hydrocarbons. 

Bicyclic  and  Tricyclic  Non-benzenoid  Hydrocarbons. 

Camphene,  bornylene  and  the  pinenes  are  bicyclic  hydrocarbons 
which  might  be  considered  as  derivatives  of  cyclohexane  but  on 
account  of  their  importance  and  the  volume  of  their  literature  these 
hydrocarbons  are  considered  in  separate  chapters.  The  three  simplest 
bridged  cyclohexane  hydrocarbons  are  not  known. 


\ 
C 
H 

norcamphane 


H 

norpinane 


These  hypothetical  hydrocarbons  have  the  cyclic  structures  of  cam- 
phene,  pinene  and  carene  respectively.  A  ketone  having  the  structure 
of  norpinane  has  recently  been  made  by  heating  the  calcium  salt  of 
cyclohexane-1.3-dicarboxylic  acid  and  it  would  probably  not  prove 
difficult  to  prepare  the  hydrocarbon  from  the  ketone.  Norpinane  and 
particularly  norcarane  would  probably  prove  to  be  unstable,  lacking 
the  gem.  dimethyl  group.1 

When  indene  is  reduced  by  sodium  and  alcohol,  two  atoms  of 
hydrogen  are  added,  forming  hydrindene,  a  large  number  of  deriva- 
tives of  which  are  known.  Willstatter  and  King  noted  that  the  double 

*Cf.  Ingold,  J.  Ohem.  8oc.  119,  952    (1921). 

396 


CYCLIC  NON-BENZENOID  HYDROCARBONS  397 

bond  in  styrene  was  reduced  by  hydrogen  and  platinum  very  much 
more  rapidly  than  the  benzene  ring  and  by  interrupting  the  hydro- 
genation  good  yields  of  ethylbenzene  could  be  obtained.  Similarly, 
indene  may  be  hydrogenated  in  contact  with  nickel  at  200°  to  hydrin- 
dene,2  boiling-point  177°.  At  300°,  in  contact  with  nickel  and  hydro- 
gen, hydrindene  is  not  further  hydrogenated  but  is  partly  decomposed 
and  partly  converted  to  indene  and  hydrogen.  At  250°-260°,  in  the 
presence  of  nickel  oxide  and  hydrogen  under  110  atmospheres  pres- 
sure, indene  and  hydrindene  are  completely  reduced  to  octohydroin- 

dene,3  a  stable  oil,  boiling-point  165°-167°    (757mm.),  dono  0.8334, 

20 

UD  1.46287. 

Santene,  C9H14.  This  hydrocarbon,  discovered  in  oil  of  sandal- 
wood  by  Miiller 4  and  in  Siberian  pine-needle  oil  by  Aschan  5  is  note- 
worthy as  being  one  of  the  few  hydrocarbons,  occurring  in  essential 
oils,  having  other  than  ten  or  fifteen  carbon  atoms.  Santene  is  char- 
acterized by  the  formation  of  a  nitrosochloride  melting  at  109°-110°, 
a  nitrosite  melting  at  125°  and  a  hydrochloride  melting  at  80°-81°. 
The  alcohol,  santenol,  formed  by  treating  with  glacial  acetic  and  su!- 
furic  acids  (Bertram  and  Walbaum's  method)  melts  at  97°-98°  and 
distills  at  195°-196°  (phenylurethane  melting  at  61°-62°).  The 
acetate  has  an  odor  resembling  bornyl  acetate  and  distills  at  215°- 
219°.  The  physical  properties  of  santene  noted  by  different  observers 
are  as  follows. 


Boiling-point    31  °-33.°(9mm.)  140.° 

d    0.863  0.8698(15°) 

20° 
n   1.46658  1.4696 

D 

The  constitution  of  santene  has  been  shown  by  Semmler  and  Bar- 
telt 8  by  means  of  oxidation  by  ozone  and  by  permanganate  in  dilute 
acetone  to  be  as  represented  in  the  following, 

2  Padoa  &  Fabris,  J.  Chem.  Soc.  A6«.  1908,  I,  255. 
*Ipatiev,  J.  Ru88.  Phys.-Chem.  Soc.  45,  994   (1913). 
*Arch.  Pharm.  238,  366   (1900). 
6  Ber.  40,  4918    (1907). 

6  Santene  from  sandal-wood  oil,  Semmler,  Ber.  40,  4591   (1907). 

7  Santene  from  Siberian  pine-needle  oil,  Ashcan,  Ber.  40,  4918  (1907). 
•Ber.  41,  385,  866   (1908). 


398       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


glycol,  M.-P.  193' 


the  constitution  being  clearly  indicated  by  the  formation  of  cyclo- 
pentane  £rarw-dicarboxylic  acid  melting-point  86°,  which  acid  was 
previously  known.  The  formation  of  santene  from  camphenilone  has 
recently  been  accomplished  by  Komppa  and  Hintikka  9  by  decompos- 
ing the  corresponding  alcohol,  camphenilol,  by  sodium  acid  sulfate  and 
also  by  heating  camphenilyl  chloride  with  aniline.  A  mixture  of 
hydrocarbons  is  obtained  but  santene  is  the  principal  product.  A 
little  confusion  is  cleared  up  by  Komppa  and  Hintikka  by  showing 
that  santenol  is  identical  with  isocamphenilol  and  Semmler's  n-nor- 
borneol,  and  that  santenone  is  identical  with  isocamphenilone  and 
Semmler's  jt-norcamphor.  In  the  conversion  of  camphenilone  or 
camphenilol  a  rearrangement  occurs,  such  as  is  frequently  observed 
among  the  terpenes  and  cyclohexane  derivatives. 


0 


camphenilone 


camphenilol 


santene 


Sabinene  and  Thujene  may  be  considered  as  derivatives  of  para- 
menthane  but  they  are  both  bicyclic  and  the  bridged  ring,  common  to 
both  hydrocarbons,  is  a  three  carbon  ring.  Thujene  (Semmler's  tan- 


9  Butt.  8oc.  cMm.  21,  13   (1917). 


CYCLIC  NON-BENZENOW  HYDROCARBONS 


399 


acetene)  has  not  been  found  in  any  essential  oil  but  sabinene  occurs 
in  the  essential  oil  of  savin  and  as  a  subordinate  constituent  in  a 
number  of  other  essential  oils.  Sabinene  purified  by  fractional  dis- 
tillation, carried  out  by  Schimmel  and  Company,  showed  a  boiling- 
point  of  163°-164°  and  an  optical  rotation  of  [a]  +  63°.  Although 

the  active  hydrocarbon  does  not  appear  to  have  been  obtained  in  a 
high  degree  of  purity,  it  can  be  differentiated  from  other  hydrocarbons 
of  approximately  this  boiling-point,  by  its  low  specific  gravity  0.8480 
(15°).  The  molecular  refraction  owes  its  exaltation  over  the  calcu- 
lated value  C^H^/^1  to  the  presence  of  the  three  carbon  ring. 
M  (observed)  44.88,  calculated,  43.53.  It  is  readily  converted  to  1.4- 
terpin,  terpinenol  (4)  and  terpinene  by  the  action  of  dilute  sulfuric 
acid. 

On  oxidation  by  alkaline  permanganate  sabinene  behaves  very 
much  like  p-pinene  and  other  substances  having  a  semicyclic  methene 
group;  it  yields  first  sabineneglycol  (melting-point  54°),  then  sabi- 
nenic  acid,  the  sparingly  soluble  nature  of  the  sodium  salt  making 
its  isolation  easy.10  Sabinenic  acid  melts  at  57°  and  on  further  oxida- 
tion by  lead  peroxide  and  sulfuric  acid  yields  sabina  ketone.11  The 
three  carbon  ring  in  sabina  ketone  is  readily  broken  by  hydrogen 
chloride  in  methyl  alcohol  and  when  the  product  is  heated  with 
aniline  two  isopropylcyclohexenones  are  produced.  These  ketones 
have  been  useful  as  serving  for  the  synthesis  of  ct-terpinene  and  a  and 
(3-phellandrene. 


CH 


sabinene 


glycol 
M.-P.  54° 


sabinenic  acid 
M.-P.  57° 


sabina 
ketone 


"Wallach,  Ann.  359,  266    (1908). 

11  Sabina  ketone  boils  at  218° -219°  and  yields  a  semicarbazone  melting  at  141°-142V 


400      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

0 


Thujene  has  been  made  indirectly  from  thujone,  a  ketone  occuring 
in  the  oils  of  thuja,  wormwood,  tansy  and  sage.  (The  ketone  has 
also  been  called  tanacetone.)  The  ketone  can  be  isolated  by  its  bisul- 
fite compound,  using  ammonium  bisulfite  and  adding  a  little  alcohol 
to  increase  the  solubility  of  the  ketone,  and  allowing  to  stand.  The 
ketone  may  be  liberated  from  the  crystalline  bisulfite  compound  by 
adding  alkali  and  distilling  with  steam.  There  are  two  physically 
isomeric  thujones,  designated  as  a  and  (3,  and  when  they  occur  to- 
gether they  can  be  separated  by  fractional  crystallization  of  the 
semicarbazones  and  regeneration  of  the  ketones  from  the  purified 
semicarbazones.  The  a-thujone,  which  is  the  chief  ketone  in  thuja 
oil,  boils  at  200°-201°,  specific  gravity  0.9125,  [a]  —  10°  23'  and 


1.4510.    It  appears  to  yield  two  dextro-rotatory  semicarbazones 


melting  at  110°  and  186°-188°.  Heating  with  alcoholic  caustic  alkali 
or  alcoholic  sulfuric  acid  converts  a-thujone  partially  into  p-thujone. 
When  p-thujone  is  liberated  from  its  semicarbazone  (melting-point 
170°-172°  or  174°-176°)  it  is  dextro-rotatory  [a]  +  76.16°.  Its 

oxime  melts  at  54°-55°.  The  conversion  of  a  to  P-thujone  by  alco- 
holic alkali  is  reversible.  Both  ketones  yield  the  same  bisulfite 
compound. 

When  the  three-carbon  ring  of  thujone  is  broken  by  heating  with 
40  per  cent  sulfuric  acid  an  isomeric  ketone,  isothujone  (boiling-point 
231°-232°,  d  0.9285)  is  formed,  which  change  is  represented  by  Wal- 
lach 12  and  by  Semmler 13  as  follows, 


"Ann.  323,  371   (1902). 
"Ber.  S3,  275,  2454   (1900). 


CYCLIC  NON-BENZENOID  HYDROCARBONS 
CHS  CM,  0 

=0 


401 


isothujone 

Hydrogen  chloride  breaks  the  three-carbon  ring  in  a  different  manner, 
a-thujene  giving  terpinene  dihydrochloride.14  Isothujone  yields  two 
physically  isomeric  thuj  amenthols  according  to  whether  the  reduction 
is  carried  out  by  sodium  and  alcohol  (a-thujamenthol,  boiling-point 
212°-214°,  d  0.8990)  or  by  hydrogen  and  palladium  which  yields 

p-thujamenthone  and  then  by  farther  reduction  by  alcohol  and  sodium 
p-thujamenthone15  yields  the  p-alcohol,  which  boils  about  2°  higher 
than  the  a-form.  Thuj  one  may  be  reduced  to  the  corresponding  alco- 
hol, thujyl  alcohol  (boiling-point  210°-212°,  dono  0.9265),  which 

«U 

alcohol  is  also  formed  by  the  action  of  nitrous  acid  on  thujyl  amine 
(the  yields  of  alcohol  by  this  reaction  in  most  cases  are  very  poor). 
Thujylamine  is  obtained  in  the  usual  manner,  by  reduction  of  thu- 
jone  oxime.  Oxidation  of  thuj  one  yields  first  a  keto  acid,  melting- 
point  75°-76°,  and  then  by  further  oxidation  a  dicarboxylic  acid  melt- 
ing at  141°-142°,  both  still  retaining  the  three  carbon  ring  but  the 
.cyclopropane  ring  is  much  more  stable  in  the  dicarboxylic  acid. 


COW 


C02H 


a-thujaketonic  acid 
M.-P.  75°-76°  labil 


a-dicarboxylic  acid 
M.-P.  141°-142°  stable 


"  Wallach,  Ann.  360,  97. 


402       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

The  constitution  of  thujene  has  not  yet  been  clearly  shown  but  it 
is  believed  to  be  as  follows, 


The  physical  properties  of  the  hydrocarbon,  prepared  by  different 
methods,  indicate  that  "thujene"  is  probably  a  mixture  of  hydrocar- 
bons, one  of  which  probably  has  the  constitution  shown  above.  The 
name  was  formerly  applied  to  the  hydrocarbon  made  by  the  dry  dis- 
tillation of  the  hydrochloride  of  thujylamine  or  isothujylamine. 
Tschugaeff  prepared  thujene  by  heating  thujyl  xanthogenate,  and  also 
by  heating  and  decomposing  trimethylthujyl-ammonium  hydroxide, 
the  latter  method  giving  a  hydrocarbon  of  considerably  higher  optical 
rotation  than  the  former.  The  highest  rotation  observed  is  that 
noted  by  Kondakow  and  Skworzow,16  i.e.,  +  109°.  The  following 
physical  properties  have  been  noted, 

Observer  Boiling-Point  Density  16°  n 

D 

Semmler "    60°-  63°  (14mm.)  0.8508  1.4760 

Wallach    170°-172°  (760mm.)  0.8360  1.47145 

Tschugaeff "   151  °-152°  (670mm.)  0.8275  1 .45042 

Thujane  was  made  by  Tschugaeff  and  Formin 19  by  catalytic 
hydrogenation,  in  the  presence  of  platinum,  of  the  thujene  made  by 
decomposing  thujylmethyl  xanthogenate.  Thujane  is  readily  oxidized 
by  permanganate.  Sabinene  also  gives  the  same  hydrocarbon  by 
hydrogenation  under  the  same  conditions.  The  following  physical 
properties  were  noted,  boiling-point  157°  (758  mm.),  dlfio  0.8190,  Mol. 

19Chem.  Zentr.  1910,  II,  467. 
» Ber.  25,  3345   (1892). 
"Ber.  33,  3118   (1900). 
19Compt.  rend.  151,  1058   (1910). 


CYCLIC  NON-BENZENOID  HYDROCARBONS 


403 


Refraction^   44.54  to  44.80,  calculated  43.92,  the  difference  being 

attributed  to  the  presence  of  the  cyclopropane  ring.  Thujane  pre- 
pared by  Kishner20  from  thujone  by  his  hydrazine  method  showed 
the  following  physical  properties,  boiling-point  157.5°  (741  mm.),  d 

0.8164,  [a]D  +53.41,  nD  1.4398. 

Carene:  This  terpene,  recently  found  in  Indian  turpentine  (from 
Pinus  longifolia,  Roxb.)  is  one  of  the  few  hydrocarbons  occurring  in 
nature  which  contains  a  three-carbon  ring.  It  has  frequently  been 
noted  that  this  turpentine  contained  a  terpene  which  yields  sylvestrene 
hydrochloride  and  it  is  usually  stated  that  sylvestrene  is  present  in 
this  oil,  although  Robinson 21  stated  that  the  terpene  was  probably  an 
isomer  of  sylvestrene.  Simonsen  22  isolated  the  hydrocarbon,  boiling- 
point  168°-169°  (750mm.)  by  fractional  distillation,  and  had  no  diffi- 
culty in  preparing  d-sylvestrene  hydrochloride  from  this  fraction.  The 
liquid  hydrochloride  mixture  gave  sylvestrene  and  dipentene  on  heat- 
ing with  sodium  acetate  in  acetic  acid.  Oxidation  by  permanganate 
gave  a  glycol  melting  at  69°-70°  which  apparently  contains  no  pri- 
mary alcohol  group  indicating  the  absence  of  the  methene  group. 
Oxidation  by  permanganate  under  the  conditions  recommended  by 
Baeyer  and  Ipatiev  gave  trans-caronic  acid,  from  which  facts  Simon- 
sen  concludes  that"  carene  has  one  of  the  two  following  structures,  or 
is  perhaps  a  mixture  of  the  two. 


30° 

d.  Carene  is  slightly  dextro-rotatory,   [a]      +  7.69°,   D -  0.8586, 

30° 
n_  1.469  and  from  the  refractive  index  M  44.23;  M  calculated  for 

*°J.  Ruas.  Phys.-Chem.  Soc.  42,  1198  (1910). 
J1Proc.  Chem.  Soc.  27,  247   (1911). 
21 J.  Chem.  Soc.  in,  570    (1920). 


404       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

doH^/^1  =  43.5  and  adding  the  increment  usually  observed  in  cases 
where  a  cyclopropane  ring  is  present  M  calc.  becomes  43.5  +  0.69 
=  44.19. 

Naphthalene  is  readily  hydrogenated  in  the  presence  of  finely 
divided  platinum.  When  dihydronaphthalene  is  employed  as  the 
raw  material,  two  atoms  of  hydrogen  are  very  rapidly  taken  up  and 
if  the  hydrogenation  is  then  interrupted  a  good  yield  of  tetrahydro- 
naphthalene  can  be  obtained  but  when  starting  with  naphthalene  and 
stopping  the  operation  after  four  atoms  of  hydrogen  had  been  taken 
up,  the  product  was  found  to  be  a  mixture  of  unchanged  naphthalene 
and  decahydronaphthalene.23 

Tetrahydronaphthalene  and  the  completely  hydrogenated  decahy- 
dronaphthalene were  widely  used  in  Europe,  during  the  war  period,  as 
solvents,  particularly  as  paint  and  varnish  thinners.24  A  mixture  of 
the  hydrocarbons  is  manufactured  under  various  trade  names.  Their 
solvent  values  are  not  accurately  known  but  they  are  miscible  with 
petroleum  oils  and  are  good  solvents  for  coumarone  resin,  many 
natural  resins,  waxes,  fats  and  oils.  Their  manufacture  appears  to 
be  carried  out  in  accordance  with  the  well-known  conditions  of  hydro- 
genation, employing  temperatures  within  the  range  120°-150°,  and 
pressures  within  the  range  3  to  100  atmospheres.25  A  preliminary 
purification  from  sulfur  compounds  by  heating  with  metallic  sodium, 
or  with  sodium  amide  is  advised.26  Tetrahydronaphthalene  distills 

at  205°-207°,  d1  K0  0.975,  flash-point  78°.    Decahydronaphthalene  dis- 
lo 

tills  at  189°-191°,  d2QO  0.8827,  flash-point  57.30.27    Auwers  28  notes 

the  molecular  refraction  (D  line)  of  tetrahydronaphthalene  as  42.91 
and  that  of  decahydronaphthalene  as  43.85. 

The  action  of  bromine  on  tetrahydronaphthalene  is  of  interest  as 
indicating  the  relative  ease  of  bromine  substitution  in  the  two  types 
of  rings.  No  reaction  takes  place  in  the  dark  except  in  the  presence 
of  a  catalyst  such  as  iron  or  iodine  when  substitution  in  the  benzene 
ring  takes  place.  At  higher  temperatures,  or  in  the  light,  the  reduced 
ring  is  rapidly  attacked  but  the  only  product  isolated  was  a  p-dibromo- 
tetrahydronaphthalene 29  (melting-point  70°). 

28  Willstatter  &  King,  Ber.  46,  527    (1913). 

**  Frydlender,  Rev.  prod.  chim.  23,  437   (1920). 
"Brit.  Pat.  147,474    (1920). 
2«Brit.  Pat.   147,488    (1920);   147,580    (1920). 
"Vollman,  Farter  Ztg.  24,  1689   (1919). 
"Ber.  46,  2988   (1913). 

29  v.  Braun  &  Kirschbaum,  Ber.  5$,  597   (1921). 


CYCLIC  NON-BENZENOID  HYDROCARBONS  405 

The  alcohols  a  and  p-naphthanol  were  prepared  by  Ipatiev  by  his 
high  pressure  method.30  0-Naphthanol  C10H17.OH  distills  at  242°- 
244°  and  melts  at  99°-100°;  a-naphthanol,  C10H17OH,  distills  at 
245°-250°  and  melts  at  57°-59°,  but  Mascarelli81  states  that  this 
alcohol  can  be  separated  into  two  stereo-isomers  melting  at  75°  and 
103°.  Both  alcohols  resemble  cyclohexanol  and  the  aliphatic  sec- 
ondary alcohols  in  their  chemical  behavior.  Naphthane-2  .  2-diol  has 
been  obtained  in  cis  and  trans  forms;  by  the  action  of  dilute  caustic 
potash  on  2  .  2-dibromonaphthane  the  cis  form  melting  at  160°  is 
obtained,  while  silver  acetate  on  the  dibromide  yields  the  trans  diol, 
melting  at  1410.32 

The  ketone  |3-naphthanone  has  been  very  little  studied  but  evi- 
dently undergoes  the  reactions  of  ether  alicyclic  ketones.  Darzens 
and  Leroux33  condensed  (3-naphthanone  with  chloroacetic  ester  in  the 
presence  of  sodium  ethylate  to  the  glycidic  ester,  the  free  acid  from 
which  loses  carbon  dioxide  on  distillation  giving  p-naphthanoic  alde- 
hyde (boiling-point  95°-96°  at  3  mm.). 

H2         H2  H2        H2 

C          C  CO 

/  \H/  \  /  \H/  \      H 

H2C          C          C  =  0  H2C          C          C< 

-*RC  —  CH.C02R-»  I     CHO 

H2C          C          CH2  0  H2C          C          CH2 

' 


\  /H\  /  '  \  /H\ 

C  C  C  C 

H2         H2  H2         H2 

a,  a-Dicyclohexylethane,  <IZ>  —  CH2CH2  —  <H>  This  hydro- 
carbon was  made  by  Sabatier  and  Murat34  by  the  hydrogenation  of 
diphenylethane  in  the  presence  of  catalytic  nickel  and  hydrogen  at 
220°.  Its  physical  properties  are  as  follows:  Boiling-point  256°-257°, 

40° 
d2flo0.8271,ns-  1.511. 

The  Nomenclature  of  spiro  and  other  bridged  ring  hydrocarbons 
is  in  a  very  unsatisfactory  state  and  none  of  the  systems  thus  far 
proposed  are  very  satisfactory  except  for  certain  types  or  classes  of 
hydrocarbons.  Probably  the  most  flexible  and  least  confusing  is  that 

80  Per.  40,  1288   (1907). 

11  Chem.  Alts.  1912,  83. 

"Leroux,  Compt.  rend.  148,  1614   (1909). 

nCompt.  rend.  154,  1812   (1912). 

"Compt.  rend.  154,  1771  (1912), 


406       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

recently  proposed  by  Beesley  and  Thorpe.  The  scheme  advocated  by 
Baeyer85  rests  upon  the  fact  that  all  dicyclic  systems  contain  three 
bridged  rings  which  makes  it  possible  to  distinguish  them  by  prefixed 
numerals  such  as  (0.1.2),  (1.2.3),  (0.1.4)  and  so  on,  depending 
upon  whether  the  "bridge"  is  formed  by  the  linking  of  two  tertiary 
carbon  atoms  (0),  or  whether  it  is  itself  formed  by  1,2  or  more  carbon 
atoms.  When  Baeyer's  system  is  extended  to  tricyclic  substances  it 
becomes  exceedingly  cumbersome  and  complex.  The  plans  suggested 
by  Borsche 36  and  by  Bredt  and  Savelsberg 37  are  open  to  the  objection 
that  terms  such  as  methylene  are  used  to  denote  ring  formation  and 
not  unsaturation,  and  that  the  names  of  the  compounds  do  not  neces- 
sarily indicate  to  which  of  the  cyclic  systems  they  belong.  Thus 
pinene  by  these  systems  would  be  named  as  follows, 

Borsche.     l-Methyl-l-r-2^4>-dimethylmethylene-A1(6)-cyclohexene. 

Bredt  and  Savelsberg:  m-meso-methylene-4 . 4 . 2i3-trimethy Icyclo- 
A^-hexene. 

Beesley  and  Thorpe  (see  below) :  dimethylmethane-II1 3-4-methyl- 
A4-cyclohexene. 

The  hydrocarbon  of  the  following  structure, 
CH, CH CH, 


would  be  named,  according  to  Bredt  and  Savelsberg,  p-wesometh- 
ylene-1 .  l-dimethylcyclohexane-amphi-2a .  3a-methylene.  By  Beesley 
and  Thorpe's  system,  the  name  would  be  methane-II1-2-cyclohexane- 
1-*II-dimethylmethane.  Beesley  and  Thorpe's  system  appears  to  the 
writer  to  be  much  more  easily  grasped  and  easier  to  apply  than  the 
others, — and  much  more  definite.  It  may  be  briefly  outlined  as 
follows: 

A  compound  containing  associated  rings  may  be  of  two  kinds. 

A.  It  may  be  formed  from  a  simple  ring  compound  having  a  side 
chain  of  carbon  atoms  from  which  another  ring  is  produced  by  a  link- 
ing between  another  carbon  atom  of  the  ring  and  another  of  the  side 
chain,  thus: 

*'Ber.  S3,  3771  (1900). 
"Aim.  877,  70  (1910). 
"J.  praM.  Chem.  (2)  97,  1  (1918). 


CYCLIC  NON-BENZENOID  HYDROCARBONS 


407 


(1) 


(2) 


(3) 


In  these  cases  the  side  chain  and  the  ring  would  be  given  their  usual 
names,  the  number  of  linkings  joining  the  two  would  be  indicated  by 
a  Roman  numeral,  and  the  carbon  atoms  of  the  two  series  participat- 
ing in  the  ring  complex  would  be  indicated  by  means  of  index  figures 
on  which  the  particular  residue  is  placed.  Thus,  the  above  hydrocar- 
bons (1),  (2)  and  (3)  would  be  named  as  follows, 

(1)  is  Ethylmethane-IP  2 — cyclopentane. 

(2)  is  2-Methylethane— 12IP-2—  cyclopentane. 

(3)  is  Propane — *  3IP  2 — cyclopentane. 

The  following  is  an  example  of  the  nomenclature  of  derivatives  accord- 
ing to  this  system. 

GIL  —  CH  —  CH9 


CH2— C 


Br 


>CH  —  CH.Br 
•  CH3 


l-bromo-2-methylethane — 

^_  1.2  n  1.2  _2-bromo-4-methyl- 
cyclopentane. 


CH 

CH  CH 


I 

—  C 


H.CH3 


2-methylethane— 1-1-2— III1-2-4  — 
— cyclobutane. 


B.  The  associated  ring  may  be  considered  as  formed  by  linking 
pairs  of  carbon  atoms  in  a  ring  to  which  another  ring  is  already 
attached,  as  for  example,  the  following, 


408       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 
H9C CH2  H2C CH CH 


\  CH, 

CH  — CH<| 

CH. 


HC 


•I 


CH  —  CH 


\ 


cyclopropane-*-2  II  1-2- 
-cyclopentane 


The  only  rules  which  seem  to  be  necessary  are:  (1)  That  one  of 
the  linked  carbon  atoms  in  the  ring  should  be  called  1,  and  that  the 
corresponding  carbon  atom  in  the  chain  should  also  be  called  1.  The 
numbering  would  then  proceed  in  the  ring  clockwise,  and  in  the  side 
chain  in  the  usual  manner.  (2)  That  the  name  of  the  simplest  por- 
tion of  the  chain  entering  into  ring  formation  should  be  used  first, 
and  any  attached  groups  should  be  named  as  derivatives  of  the 
simplest  chain,  for  example, 

CH2  —  CH 
CH2  CH 

CH2  —  CH 


2-methyl— 1-2  III 1-2-6  — cyclohexane 

For  further  details  and  possible  extensions  of  the  system  to  hetero- 
cyclic  compounds,  the  original  paper  of  Beesley  and  Thorpe  should  be 
consulted.88 

8.3-Dimethyl-[0.1 .3]-Dicyclohexane:  This  hydrocarbon  was 
synthesized  by  Zelinski39  by  reducing  1 . 1-dimethylcyclohexane  3.5- 
dione  to  the  corresponding  diol,  converting  the  diol  to  the  correspond- 
ing dibromide  by  phosphorus  tribromide  and  finally  treating  the  dibro- 
mide  with  zinc  dust  in  aqueous  alcoholic  solution.  The  chemical  and 
physical  properties  of  the  resulting  hydrocarbon,  boiling-point  115° 

20°                   20° 
(corr),  d — —  0.7962,  n 1.4331,  particularly  when  compared  with 

the  isomeric  1 .  l-dimethyl-A8-cyclohexene  led  Zelinsky  to  propose 
the  bicyclic  structure  shown  below.  The  three  carbon  ring  is  broken 
in  two  ways  under  different  conditions.  (1)  By  heating  with  hydri- 
odic  acid  to  give  a  hydrocarbon  boiling  at  115°-116°  and  indifferent 
to  bromine  and  permanganate,  probably  1.1.3-trimethylcyclopentane, 
and  (2)  by  catalytic  hydrogenation  in  the  presence  of  platinum  black, 

88  J.  Chem.  Soc.  117,  591    (1920), 
88  Ber.  $6,  1466    (1913). 


CYCLIC  NON-BENZEN01D  HYDROCARBONS  409 

yielding  a  hydrocarbon  distilling  at  109.5°-110.5°;  which   Zelinski 
claims  is  l-methyl-2-isobutylcyclopropane. 

CH  — CH2  CH2  — CH2 

/I                \       CH3  \      CH3 

H2C                          C<  — >    CH3                        C< 

\                  /       CH3  \|                  /      CH3 

CH  — CH,  CH  —  CH2 


CH  — CH3 

\    H2C<|  CH3 

CH  — CH2  — CH< 

CH3 

The  stability  of  this  hydrocarbon  to  heat  was  not  investigated  but 
it  is  acted  upon  rather  energetically  by  concentrated  sulfuric  acid. 
A  similar  dicyclohexane  derivative  was  discovered  by  Kishner,40 
in  quite  a  different  manner.  When  camphophorone  is  treated  with 
hydrazine  a  pyrazolone  base  is  first  formed,  which  on  heating  with 
caustic  potash  yields  the  hydrocarbon  2.6.6.-trimethyl-[0.1 .3.]- 
dicyclohexane.  It  has  a  petroleum-like  odor,  boils  at  140°  (752  mm.), 

20° 
d  — -  0.8223 ;  does  not  decolorize  permanganate,  dissolves  in  fuming 

nitric  acid  and  reacts  with  hydrogen  bromide  to  give  a  bromomethyl- 
isopropylcyclopentane. 

CH2 — CH2  CH3 

>CH— C<        +  KOH  CH2— CH2— CH 

CH3-CH-CV  I     CH,-      -*  /\    CH3 

X  N  —  NH  CH3— CH  — CH  — C  < 

CH3 
HBr 


CH2  —  CH2  —  CH2 

CH3  — CH  —  C 

H\ 

CBr.(CH3)2 

Caryophellene:  The  hydrocarbon  oil  described  in  the  older  litera- 
ture under  this  name  has  been  shown  by  Deussen  and  his  students  to 
be  a  mixture  of  at  least  two  and  probably  three  hydrocarbons.  The 

40  J.  Rues.  Phya.-CJiem.  Soc.  kk>  849    (1912). 


410       CHEMISTRY  Of  THE  NON-BENZENOID  HYDROCARBONS 

hydrocarbon  mixture,  isolated  from  copaiba  balsam,  clove  oil  and 
other  essential  oils,  which  distills  at  about  258°-261°,  d  0.905  to  0.910 
and  which  yields  a  crystalline  dihydrochloride  (by  passing  dry  HC1 
into  a  dry  ethereal  solution)  melting  at  69°-70°,  has  been  called 
caryophellene.  The  easiest  crystalline  derivative  to  prepare  is  caryo- 
phellene  alcohol,  C15H260,  readily  prepared  from  the  hydrocarbon  by 
Bertram  and  Walbaum's  method.  The  alcohol  melts  at  94°-96°  and 
yields  a  phenylurethane,  melting  at  136°-137°. 

The  work  of  Deussen  and  others  on  caryophellene  clearly  shows 
the  difficulties  of  working  with  mixtures  of  hydrocarbons  and  the 
almost  impossible  task  of  determining  the  constitution  of  such  sub- 
stances when  present  together  and  when  they  cannot  easily  be  sepa- 
rated. It  is  worth  while  to  examine  Deussen's  work  as  indicating 
to  a  limited  extent  the  difficulties  with  which  one  would  be  confronted 
in  attempting  to  ascertain  the  structure  of  the  hydrocarbons  occurring 
in  the  higher  boiling  distillates  of  petroleums.41 

Wallach  obtained  a  crystalline  nitrosochloride  melting  at  161°- 
163°  from  the  hydrocarbon  fraction  boiling  at  250°-270°,  derived 
from  oil  of  cloves.  Kremers  and  Schreiner  prepared  the  nitrosochlo- 
ride and  after  reacting  with  benzylamine,  were  able  to  separate  the 
nitrolbenzylamine  by  fractional  crystallization  into  fractions  melting 
at  167°  (named  a-caryophellenenitrolbenzylamine)  and  at  128° 
(named  (3-caryophellenenitrolbenzylamine).  Deussen42  found  that 
by  heating  the  crude  nitrosochloride  in  alcohol,  cooling  and  separating 
the  crystals,  the  melting-point  was  raised  to  177°-179°.  The  behavior 
of  the  nitrosochlorides  led  Deussen  to  suspect  the  presence  of  one  or 
more  other  hydrocarbons.  Repeated  fractional  distillation  43  resolved 
the  crude  caryophellene  into  three  fractions,  fractions  I  and  III  hav- 
ing different  optical  rotation  and  slightly  different  boiling-points,  but 
otherwise  very  much  alike, 

/  /// 

Boiling-point   ..     132.°-134.°(16mm.)  123.°-124.°  (14.5mm.) 

Ca]D —4.67°  —25.03° 

d  2Q 0.90346  0.8990 

n  D 0.49973  1.49617 

MR    .                                                 66.45  66.31 

MR  (for  /=2) 66.15 

41  It  is  the  writer's  belief  that  the  only  practical  way  of  throwing  any   light  on 
the  character  of  such  petroleum  hydrocarbons  is  to  synthesize  hydrocarbons  of  different 
types  and  compare  the  properties  of  such  synthetic  hydrocarbons  with  close  cut  petro- 
leum fractions. 

42  Ann.  356,  5    (1907). 
**Ann.  859,  246   (1908). 


CYCLIC  NON-BENZENOID  HYDROCARBONS 


411 


Fraction  I.  was  believed  to  be  inactive,  so-called  a-caryophellene  con- 
taminated with  a  small  proportion  of  the  laevo-p-caryophellene.  The 
latter  hydrocarbon  yields  a  blue  nitrosite  from  which  Deussen  con- 
cludes4* (from  Baeyer's  work  on  terpinolene)  that  p-caryophellene 
contains  a  double  bond  of  the  type  shown  in  the  following  structure, 
which  he  proposed. 

CH3 
I          H2 

CH      C 


HC 


H2C 


CH 


CH 


ft      HH 


CH 


When  an  excess  of  N203  (from  the  reaction  of  arsenious  acid  and 
nitric  acid)  is  passed  into  an  ethereal  solution  of  caryophellene  a  blue 
color  first  appears,  followed  by  the  formation  of  a  voluminous  yellow- 
ish white  precipitate  and  the  discharge  of  the  blue  color,45  this  be- 
havior resembling  the  formation  of  caoutchouc  nitrosite.46  The  volu- 
minous precipitate  from  caryophellene  crystallizes  from  ethyl  acetate 
in  silky  needles  melting  with  decomposition  at  159°-160°,  the  separa- 
tion of  this  substance  being  regarded  by  Deussen  as  a  delicate  test  for 
P-caryophellene.  The  formation  of  this  substance  is  attended  by  the 
removal  by  oxidation  of  the  isopropyl  group. 

c_  NO 

I 

C  —  ONO 
/\ 
CH3        CH3 


CH 


TT 

..I....  ONO 
C/ 
\ 

CH2NO 


HC  —  ONO 

+  C3  residue 


Deussen  advanced  this  explanation  of  the  change  by  reason  of  the 
fact  that  the  product  is  soluble  in  alkali,  a  property  only  of  primary 


"Ann.  369,  55  (1909). 

48  Deussen,  Ann.  388,  138   (1912). 

"Harries,  Ann.  383,  198  (1911). 


412       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

and  secondary  nitro  derivatives.     Deussen47  represents  the  deriva- 
tives of  a  and  |3-caryophellene  diagrammatically  as  follows, 

a-caryophellene 

(Humulene)  \        \ 

/  \        \ 

nitrosochloride  nitrosate      nitrosite 

M.-P.  177°  M.-P.  161°  M.-P.  116° 

+  Na  ethylate    \  j 

initrolbenzylamine 
M.-P.  126°-128° 
nitrosocaryophellene 
M.-P.  128° 

p-caryophellene 

glycol  /        /  \     \ 

M.-P.  120.5°        /          nitrosite    dihydrochloride 
y  M.-P.  115°    M.-P.69°-70° 


nitrosochloride 
M.-P.  159°       / 


\  \ 

\  \ 


\  \ 

N306     isocaryophellene 

nitrolbenzylamine\    M.-P.  159.5°  \ 

M.-P.  172°-173°      \  \ 

a-form        < nitrosochloride 

M.-P.  122°  M.-P.  120° 
\ 


p-form 
M.-P.  146° 

Although  Semmler  and  Mayer 48  have  proposed  structural  formulae  for 
what  he  terms  (using  a  curious  nomenclature  of  his  own)  Terp-caryo- 
phellene  and  Lim-caryophellene,  these  structures  can  hardly  be  con- 
sidered as  proven  and  will  not  be  given  space  in  this  brief  review. 
The  above  outline  will  indicate  the  variety  of  the  isomeric  derivatives 
and  the  difficulty  of  clearing  up  the  constitution  of  such  mixtures  of 
oils.  Humulene  is  the  name  given  by  Chapman  to  a  sesquiterpene 
fraction  isolated  from  oil  of  hops,  but  Deussen  considers  it  to  be 
identical  with  a-caryophellene. 

Cadinene  is  the  name  given  to  a  hydrocarbon  or  rather  a  mixture  of 

"Ann.  369,  41   (1910). 

"Ber.  J,3,  3451   (1910)  ;  44,  3651   (1911). 


CYCLIC  NON-BENZENOID  HYDROCARBONS  413 

hydrocarbons  occurring  in  camphor  oil,  cedar  wood  and  other  essen- 
tial oils;  it  is  characterized  by  the  formation  of  a  dihydrochloride 
melting  at  117°-118°  and  this  dihydrochloride  may  be  prepared  from 
the  crude  hydrocarbon  mixture  distilling  at  260°-280°.  Pure  cadi- 
nene  has  never  been  obtained  from  natural  oils  but  the  sesquiterpene 
regenerated  from  the  dihydrochloride  (which  is  perhaps  not  identical 
with  the  natural  hydrocarbon)  is  usually  regarded  as  nearly  pure 
"cadinene."  The  hydrocarbon  may  be  prepared  by  decomposing  the 
dihydrochloride  by  the  usual  methods,  heating  with  alcoholic  caustic 
alkali,  with  aniline,  or  with  sodium  acetate  in  acetic  acid.  The 
physical  properties  of  regenerated  cadinene  are  as  follows, 

I*  n"  III51 

Boiling-point    274.°-275.°  271.°-273.°  271.°-272.° 

d^o 0.918  0.9215(15°)  0.9183 

[alD —98.56°  -105.°  30'  —111.° 

nD    1.50647  1.5073 

Dextro-rotatory  cadinene  has  been  observed  in  the  essential  oil  of  the 
Atlas  cedar. 

Cadinene  resinifies  very  rapidly  and  is  very  easily  polymerized, 
an  indication  that  the  two  double  bonds  are  in  conjugated  positions. 
The  dihydrobromide,  melting-point  124°-125°,  and  the  dihydroiodide, 
melting  at  105°-106°,  are  best  made  in  glacial  acetic  acid  solution. 
By  catalytic  hydrogenation,  in  the  presence  of  platinum,  tetrahydro- 
cadinene  is  produced,  boiling  at  125°-128°  (10mm.),  d  0.8838, 

nD  1.48045. 

The  constitution  of  cadinene  is  not  known. 

By  the  distillation  of  galbanum  resin  Semmler  and  Jonas52  ob- 
tained a  sesquiterpene  alcohol,  cadinol,  which  on  decomposition  by 
potassium  acid  sulfate,  formic  acid  or  phthalic  anhydride  yields 
cadinene. 

Selinene:  A  sesquiterpene  distilling  at  262°-269°  was  discovered 
in  oil  of  celery  seed  by  Ciamician  and  Silber 53  and  the  hydrocarbon 
was  later  recognized  as  a  new  hydrocarbon  by  Schimmel  &  Co.,54 
who  characterized  it  by  the  formation  of  a  dihydrochloride  melting 

"Wallach,  Ann.  252,  150    (1889)  ;  271,  297   (1892). 

60  Schimmel  &  Co. ;  Gildemeister,  "Die  Aetherischen  Oele,"  Ed.  II,  Vol.  I,  347. 
61 J.  Russ.  Phys.'Chem.  Soc.  40,  698   (1908). 

82  Ber.    47.    2068     (1914).     Cadinol    distills    at    155°-165°     (15mm.),    d  09720 

[a]  D  +  22°. 

63  Ber.  SO,  496   (1897). 

"Schimmel  &  Co.  Semi-Ann.  Rep.  1910  (1),  32. 


414       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

at  72°-74°.  Semmler  and  Risse55  prepared  the  dihydrochloride  (by 
HC1  into  the  ethereal  solution)  and  regenerated  what  they  regard  as 
selinene,  identical  with  the  original  hydrocarbon  but  purer,  by  decom- 
posing the  dihydrochloride  by  alcoholic  caustic  potash.  The  hydro- 
carbon thus  obtained  distills  at  128°-132°  (11  mm.),  d2QO  0.919,  HD 

1.5092,    [a]     +61°   36'.    Reduction  by  sodium  and  alcohol  yields 

tetrahydroselinene  having  the  following  physical  properties,  boiling- 
point  125°-126°  (10  mm.),  d2QO  0.888,  MD+  1°  12',  nD  1.48375. 

By  shaking  the  dihydrochloride  with  milk  of  lime  for  36  hours 
at  95°  an  alcohol,  selinol,  C15H260,  is  formed,  which  may  be  reduced 
by  hydrogen  (Willstatter's  method)  to  dihydroselinol,  C15H280,  melt- 
ing-point 86°-87°. 

On  account  of  differences  observed  in  the  products  obtained  by 
treating  natural  and  regenerated  selinene  with  ozone  and  hydrolyzing 
the  ozonides,  Semmler  regards  natural  selinene  as  a  mixture  of  two 
hydrocarbons,  both  of  which  are  believed  to  yield  the  same  dihydro- 
chloride. Semmler  regards  these  two  hydrocarbons  as  related  to  each 
other  in  the  same  way  as  a  and  p-pinene,  the  hydrocarbon  predomi- 
nating in  natural  selinene  having  a  >C  =  CH2  group,  the  double 
bond  in  the  regenerated  selinene  being  in  the  ring.  Many  will  regard 
the  constitutions  proposed  by  Semmler  as  guesses,  perhaps  to  be 
proven  correct  by  further  work  but  not  clearly  shown  up  to  the 
present  time.  The  two  selinenes  are  bicyclic,  contain  two  double 
bonds,  and  are  believed  by  Semmler  to  be  represented  by  the  two 
following  structures, 

CH2  CH3 

H.         II  H2          | 

C  C  CO 


CH3  — C          C          CH2  CH3  — C          C          CH 

H2C          C          CH2  H9C          C! 


A  :      *•'  A 


CH3        CH2  CH3//\H2 

natural  selinene  regenerated  selinene 

"Ber.  J5,  3301    (1912)  ;  #>,  599   (1913). 


CYCLIC  NON-BENZENOID  HYDROCARBONS  415 

Eudesmene :  A  sesquiterpene  alcohol  discovered  by  Smith  56  in 
numerous  eucalyptus  oils,  and  named  eudesmol,  yields  the  sesquiter- 
pene eudesmene,  C15H24,  when  decomposed  by  heating  with  90  per  cent 
formic  acid.  The  alcohol  is  a  bicyclic  unsaturated  alcohol,  melting- 
point57  84°  and  distilling  at  156°  (10  mm.).  It  adds  two  atoms  of 
hydrogen  when  reduced  by  Willstatter's  method  (hydrogen  and  plati- 
num black  in  acetic  acid  solution)  and  the  resulting  dihydro-eudesmol 
melts  at  82°  and  distills  at  155°-160°  (12.5mm.).  When  eudesmene 
or  the  alcohol  is  treated  with  hydrogen  chloride  in  acetic  acid  a  dihy- 
drochloride,  melting  at  79°-80°,  is  formed.  The  dihydrobromide 
melts  at  104°-105°.  Eudesmene  also  combines  with  four  atoms  of 
hydrogen  when  reduced  by  the  Willstatter  method.58  The  physical 
properties  of  the  two  hydrocarbons  are  as  follows, 

Eudesmene  Tetrahydro-eudesmene 

Boiling-point    122.°-124.°(7mm.)  122.M22.50  (7.5mm.) 

d20o 0.91964  0.8893 

[a]D +  54.6°  +  10.2° 

20° 

n^- 1 .50874  0.48278 

Santalenes:  The  sesquiterpene  fraction  of  East  Indian  sandal- 
wood  oil  apparently  contains  two  hydrocarbons,  which  Guerbet 59  has 
called  a  and  (3-santalene.  Their  physical  properties  do  not  differ 
widely,  a-santalene  distilling  about  10°  lower  than  (3-santalene.  Both 
hydrocarbons  give  liquid  hydrochlorides  but  a-santalene  forms  a 
nitrosochloride  melting  at  122°  (nitrolpiperidide  melting  at  108°- 
109°)  and  P-santalene  forms  a  mixture  of  two  nitrosochlorides  which 
can  be  separated  by  fractional  crystallization  to  one  melting  at  106° 
and  another  melting  at  152°.  Probably  neither  hydrocarbon  has  ever 
been  isolated  in  a  very  pure  state.  Semmler 60  gives  the  following 
physical  properties  of  the  two  hydrocarbons. 

Boiling-Point  d^  [a]D  HD 

,-santalene      jglSftffi «««  ^  "« 

0-santa.ene      fig^f^    0.892  -35'  1.4932 

MJ.  d  Proc.  Roy.  Soc.  N.  8.  W.  S3,  86  (1899). 
"Semmler  &  Tobias,  Ber.  46.  2026  (1913).     The  melting-point  previously  recorded 
by  Semmler,  Ber.  1,5,  1390   (1912J,  was  78°. 
68  Semmler  &  Risse,  Ber.  46,  2303   (1913). 
"•Bull.  Soc.  chim.  (3)  £3,  217   (1900). 
80  Ber.  40,  3321  (1907). 


416       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

Semmler61  regards  a-santalene  as  bicyclic  and  p-santalene  as 
tricyclic. 

Associated  with  the  santalenes  in  sandal-wood  oil  are  two  alcohols, 
a  and  p-santalol,  but  their  relation  to  the  hydrocarbons  has  not  been 
shown  and  Guerbet  prefers  to  distinguish  the  hydrocarbons  formed  by 
the  decomposition  of  the  alcohols  by  the  names  a-iso  and  (3-isosanta- 
lene.  The  santalols  are  both  primary  alcohols,  yield  an  aldehyde, 
by  oxidizing  with  chromic  acid,  whose  semicarbazone  melts  at  230°. 
Oxidation  with  permanganate  yields  chiefly  tricycloeksantalic  acid, 
CnHieOg,  melting  at  71°-72°.  According  to  Guerbet  a-santalol  dis- 
tills at  300°-301°  and  p-santalol  at  309°-310°.  The  former  is  nearly 
inactive,  [a]j)  — 1.2°  and  p-santalol  has  the  rotation  [a]-£>  —  56°. 

When  a-santalol  is  reduced  by  hydrogen  in  the  presence  of  platinum 
the  hydroxyl  group  is  replaced  by  hydrogen;  the  product  is  tetra- 
hydrosantalene,62  a  bicyclic  hydrocarbon,  C15H28,  distilling  at  115°- 
116°  (9  mm.).  p-Santalol  behaves  similarly,  giving  mainly  tetrahy- 
drosantalene. 

By  heating  I.  a-phellandrene  and  isoprene  together  in  a  sealed  tube, 
Semmler  obtained  a  hydrocarbon  C15H24  boiling-point  129°-132°  (at 
15  mm.),  d20o  0.8976,  n-p  1.4949,  which  he  regarded  as  p-santalene. 

Limonene  and  isoprene  under  the  same  conditions  do  not  react.  In 
a  series  of  such  experiments  Semmler  showed  that  generally  conden- 
sation of  isoprene  with  the  terpenes  can  be  effected  at  about  275° 
but  at  330°  and  higher,  the  sesquiterpenes  are  decomposed.63 

Cedrene:  This  sesquiterpene,  occurring  in  cedar-wood  oil  associ- 
ated with  the  closely  related  alcohol,  cedrenol,  is  of  unknown  consti- 
tution although  considerable  effort  has  been  spent  in  research  on  this 
hydrocarbon.  It  forms  a  dihydrocedrene  when  catalytically  reduced 
in  the  presence  of  platinum.  Cedrene  distills  at  262°-263°,  or  124°  to 
126°  at  12  mm.,  d  0.9354,  [a]D  —55°,  n  1.50233.  Oxidation  by 

permanganate  (in  acetone  solution)  yields  a  glycol  melting  at  160°, 
also  a  diketone  or  ketoaldehyde  of  the  empirical  formula  C15H2402 
and  a  keto  acid  of  unknown  constitution,  C15H2403  (oxime  melting  at 
60° ) .  By  oxidation  of  cedrene  by  chromic  acid  in  acetic  acid  solution 
a  ketone,  cedrone,  is  produced,  this  ketone  having  a  strong  odor  of 
cedar  wood,  distills  at  147°-150.5°,  d12  5o  1.0110.64 

91  Ber.   1120    (1907). 

«8  Semmler  &  Risse,  Ber.  tf,  2303   (1913).  '     . 

"Ber.  47 f  2252    (1914). 

•*  Semmler  &  Hoffman,  Ber.  46,  768   (1913). 


CYCLIC  NON-BENZENOID  HYDROCARBONS  417 

Cedar-wood  oil  appears  to  contain  two  sesquiterpene  alcohols 
related  to  cedrene.65 

Dihydrocedrene,  obtained  from  natural  cedrene  by  catalytic  hydro- 
genation, distills  at  122°-123°  (10  mm.),  d2QO  0.9204,  HD  1.4929.  No 

crystalline  hydrochlorides  or  hydrobromides  of  cedrene  are  known. 

Tricyclic  non-benzenoid  hydrocarbons  have  been  made  by  the 
catalytic  hydrogenation  of  tricyclic  benzenoid  hydrocarbons  such  as 
anthracene  and  phenanthrene.  By  the  hydrogenation  of  phenan- 
threne  at  the  remarkably  high  temperatures  of  360°,  under  high  pres- 
sure, Ipatiev 66  obtained  the  completely  reduced  hydrocarbon  C14H24, 
which  he  calls  perhydroanthracene.  It  is  an  oil  distilling  at  270°- 
276°  and  does  not  crystallize  at  15°.  It  is  inert  to  permanganate  solu- 
tion and  bromine  in  the  cold,  and  also  practically  unacted  upon  by 
sulfuric-nitric  acid  nitrating  mixture. 

Anthracene  was  reduced  by  Godchot67  over  nickel  at  260°  to 
tetrahydroanthracene,  the  constitution  of  which  is  unknown.  It  crys- 
tallizes from  alcohol  in  plates  melting  at  89°  and  distilling  at  309°. 
At  a  little  higher  temperature,  200°-205°  octohydroanthracene,  melt- 
ing-point 71°  and  distilling  at  292°-295°,  is  formed,  and  at  260°-270° 
and  under  about  125  atmospheres  pressure  Ipatiev68  succeeded  in 
reducing  it  to  decahydroanthracene,  melting-point  73°-74°,  and  finally 
to  the  completely  reduced  hydrocarbon,  perhydroanthracene,  an  oily 
liquid. 

Copcene:  This  name  has  been  given  by  Semmler  and  Stenzel 69  to 
a  sesquiterpene  occurring,  together  with  caryophellene,  in  African 
copaiba  balsam.  The  hydrocarbon  was  separated  by  fractional  dis- 
tillation, its  constants  as  thus  isolated,  being  as  follows,  boiling-point 

119°-120°    (10mm.),  d1KO  0.9077,    [a]^    —13.35°,  n^  1.48943.    It 
lo  ±J  D 

gives  a  hydrochloride  identical  with  that  formed  by  cadinene.  The 
new  hydrocarbon  is  apparently  tricyclic,  combining  with  two  atoms 
of  hydrogen,  by  catalytic  hydrogenation  to'  give  dihydrocopaene, 
C15H26  (boiling-point  118°-121°  at  12  mm.,  nD  1.47987,  dlgo  0.8926). 

Semmler  has  proposed  a  constitution  for  copaene. 

Abietic  Acid:  Ordinary  commercial  rosin  consists  chiefly  of  abietic 
acid.  Its  constitution  is  not  definitely  known  but  it  has  been  shown 

M  Semmler  &  Mayer,  Ber.  J5,  1384   (1912). 

"Ber.  41,  999   (1908). 

"Ann.  chim.  phys.   (8)  12.  468  (1907). 

68  Ber.  41,  996  (1908). 

"Ber.  V,  255  (1914). 


418       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

to  have  the  three  ring  carbon  structure  of  phenanthrene.  Heating 
with  sulfur  forms  H2S,  carbon  dioxide  and  retene,  which  hydrocarbon 
is  believed  to  be  a  methyl  isopropyl  derivative  of  phenanthrene.  The 
fossil  substance  fichtelite,  C18H32,  is  regarded  as  completely  reduced 
retene.  Schulze 70  showed  that  rosin  oil,  obtained  by  the  destructive 
distillation  of  rosin,  contains  hydrogenated  retene  derivatives  and  by 
oxidation  1 . 2 . 4-benzene  tricarboxylic  acid  was  obtained.  The  for- 
mation of  this  acid  from  abietic  acid  would  show  that  the  methyl  and 
isopropyl  groups  are  not  attached  to  the  same  ring.  Although  com- 
bustion analyses  of  abietic  acid,  reported  by  different  observers,  agree 
almost  equally  well  with  the  empirical  formula  C19H2802  and 
C20H3002,  it  may  be  pointed  out  that  the  formula  C19H2802  agrees 
best  with  the  known  evidence  that  abietic  acid  has  the  carbon  skeleton 
of  phenanthrene  together  with  a  carboxyl  group,  a  methyl  and  an 
isopropyl  group,  or  19  carbon  atoms  in  all.  Easterfield  and  Bagley  71 
found  that  abietic  acid  was  esterified  with  difficulty  and  therefore  sug- 
gested that  the  methyl  and  isopropyl  groups  were  in  ortho  positions 
with  respect  to  the  carboxyl  group,  thus  assigning  these  two  groups 
positions  in  one  of  the  rings.  Bucher 72  has  reviewed  the  literature 
and,  in  view  of  the  character  of  the  oxidation  products,  states  that 
one  of  the  alkyl  groups  must  be  in  position  (8)  and  the  other  in  posi- 
tion (2)  or  (3).  Bucher  also  notes  that  an  alkyl  group  in  position  (2) 
and  the  carboxyl  group  in  position  (1)  would  satisfy  the  condition 
which  Easterfield  and  Bagley  believed  to  be  required  by  the  slow  rate 
of  esterification.  It  need  hardly  be  pointed  out  that  much  of  this 
rests  upon  very  slender  evidence.  As  regards  the  difficulty  of  esteri- 
fying  acids  by  saturating  an  alcoholic  solution  with  hydrochloric  acid 
gas,  it  may  be  pointed  out  that  instances  are  known  in  which  esteri- 
fication with  the  aid  of  hydrogen  chloride  proceeds  with  difficulty, 
but  with  relative  ease  when  the  alcohol  and  acid  are  heated  together. 
The  formula  C19H2802  and  the  tricyclic  structure  of  reduced  retene 
leaves  two  double  bonds  to  be  accounted  for. 

Grim,73  who  adheres  to  the  C20H3002  formula,  has  recently  pro- 
posed a  constitution  for  abietic  acid  which  has  only  one  double  bond 7* 

™Ann.  S59,  132   (1908). 

71 J.   Chem.  Soc.  85.  1238   (1904). 

72  J.  Am.  Chem.  Soc.  82,  374   (1910). 

««/.  Ctwm.  Soc.  Abs.  1921   (1),   344. 

7*  Unpublished  work  of  the  writer  has  shown  that  when  abietic  acid,  recrystallized 
from  alcohol  containing  a  little  hydrochloric  acid,  is  hydrogenated  in  dilute  alcohol  by 
Skita's  method,  the  quantity  of  hydrogen  absorbed  is  that  required  by  two  double 
bonds  (within  a  very  small  experimental  error).  This,  however,  may  nevertheless  be 
in  accord  with  Griin's  formula  and  it  may  also  be  pointed  out  that  Griin's  formula 
may  also  account  for  the  peculiar  behavior  noted  in  recrystallizing  abietic  acid.  The 


CYCLIC  NON-BENZENOID  HYDROCARBONS 


419 


and  has  a  bridged  ring  as  in  pinene,  with  which  hydrocarbon  abietic 
acid  is  associated  in  the  natural  oleo-resin.  The  formula  which  have 
been  suggested  are  as  follows, 


CH, 


COM 


Easterfield  &  Bagley 


Bucher 


(Double  bonds  not  placed) 


Grun 


Rosin  oil  has  been  manufactured  on  a  large  scale  and  the  heavier, 
neutral  fractions  used  as  a  lubricant.  As  noted  above  such  oils  con- 
tain hydrogenated  phenanthrene  or  retene  derivatives.  The  crude  oil 
contains  about  30  per  cent  by  volume  of  organic  acids,  has  a  marked 
greenish-blue  fluorescence,  and  distills  over  a  wide  range  of  tem- 
perature. Its  density  varies  from  about  0.945  to  1.010.  The  lighter 
fractions,  consisting  of  hydrocarbons  of  unknown  character,  are  some- 
times distilled  and  collected  separately,  being  known  industrially  as 
rosin  spirit.  The  fraction  distilling  at  343°-346°  is  believed  to  be  a 
diterpene,  C20H30.  Rosin  oil  resinifies  on  air  oxidation;  its  solu- 
bility in  96  per  cent  alcohol  varies  rather  widely,  i.e.,  50  to  70  per  cent 
at  ordinary  temperatures,  depending  upon  the  conditions  under  which 
the  oil  has  been  made. 

y  the 


Chapter    XII.     Bicyclic   Non-benzenoid 
Hydrocarbons. 

Turpentine  and  the  Pinenes. 

Probably  the  most  outstanding  fact  with  regard  to  turpentine  is 
its  rapidly  decreasing  production.  This  is  having  the  result  that 
turpentine  is  being  replaced  in  many  of  its  applications  by  light  petro- 
leum fractions,  particularly  in  the  case  of  paints  and  varnishes  where 
it  functions  merely  as  a  solvent.  There  are  many  industrial  uses  of 
turpentine,  however,  in  which  it  appears  to  be  indispensable,  as  in  the 
manufacture  of  artificial  camphor,  terpineol  and  dammar  varnish. 
The  extent  of  the  forests  of  the  world,  capable  of  producing  turpen- 
tine, is  well  known  and  although  the  production  of  turpentine  has  been 
rapidly  diminishing,  reasonable  sylviculture,  as  in  France,1  will  insure 
a  supply  of  turpentine  easily  adequate  for  chemical  and  other  special 
purposes.  The  United  States,  the  principal  turpentine  producing 
country,  produced  27,073,000  gallons  of  oil  of  turpentine  in  1914,  but 
only  17,737,000  gallons  in  1919  in  spite  of  a  considerable  increase  in 
the  number  of  producing  plants,  much  higher  prices  per  gallon  in 
1919  and  an  increase  in  the  output  of  "wood  turpentine"  and  similar 
products  of  about  one  million  gallons.2  At  the  present  time  the  United 
States  produces  75  per  cent  of  the  world's  turpentine  supply.  Not 
many  years  ago  the  greater  part  of  the  world's  turpentine  supply  was 
derived  from  North  Carolina  alone,  but  the  turpentine  forests  of  that 
State  have  practically  disappeared,  North  and  South  Carolina  together 
now  producing  less  than  one  per  cent  of  the  American  output.  It  is 
worth  while  to  call  attention  to  these  facts,  and  a  knowledge  of  the 
physical  properties  and  chemical  behavior  of  the  pinenes  should  be 
brought  to  bear  upon  every  important  industrial  use  of  turpentine 
with  the  object  of  conserving  the  supply  for  uses  for  which  it  is  indis- 

1  The    pine    tree    plantations    in    Southwestern    France    cover    an    area    of    about 
2.5  million  acres,  of  which  about  2  million  acres  are  privately  owned. 

2  Special   Report  on   Turpentine,    U.   S.   Bureau   of   the   Census,    Washington.   May. 
1921;  Veitch,  U.  S.  Bur.  Chem.  Butt.  898  (1920). 

420 


BICYCLIC  NON-BENZENOID  HYDROCARBONS  421 

pensable  and  also  affording  relief  by  the  substitution  of  cheaper 
material,  so  far  as  possible,  in  the  case  of  consumers  now  handicapped 
by  the  high  price  of  this  solvent. 

In  the  United  States  the  only  important  sources  are  the  long  leaf 
yellow  pine,  Pinus  palustris,  and  Pinus  heterophylla,  both  of  which 
yield  turpentine  oils  consisting  of  more  than  90  per  cent  of  the  two 
pinenes.  The  terms  gum  turpentine,  gum  spirits  or  spirits  of  turpen- 
tine refer  to  the  volatile  oil,  distilled  unchanged,  from  the  natural 
oleoresin  collected  from  the  trees.  Wood  turpentine  3  made  by  distill- 
ing the  wood  in  closed  retorts  with  steam,  or  recovered  by  extracting 
the  wood  with  a  low  boiling  solvent,  can  be  refined  so  as  to  replace 
turpentine  for  practically  all  solvent  purposes,  but  when  old  stump 
wood  is  distilled  an  entirely  different  product  is  obtained,  known  com- 
mercially as  "long  leaf  pine  oil"  or  "pine  oil,"  the  chief  constituent  of 
which  is  terpineol 4  but  other  minor  constituents  which  have  been 
identified  in  it  include  the  pinenes,  Uimonene  and  dipentene,  a  and 
y-terpinene,  borneol,  fenchyl  alcohol  and  traces  of  cineol  and  camphor. 
The  greater  part  of  such  pine  oil  distills  from  190°-220°  and  is  useful 
for  the  manufacture  of  terpin  hydrate  and  terpineol,  for  the  flotation 
of  copper  sulfide  ores  and  in  certain  solvent  mixtures  and  cleansing 
compositions.  Rosin  spirit  is  a  term  employed  for  the  mixture  of 
hydrocarbons  obtained  by  the  destructive  distillation  of  rosin.  It 
contains  very  little  of  the  pinenes,  boils  over  a  wide  range  of  tem- 
perature and  usually  contains  organic  acids  of  unknown  character;  it 
usually  gives  the  Liebermann-Storch  color  reaction  with  acetic  anhy- 
dride and  sulfuric  acid.  It  will  be  obvious  from  their  composition  that 
neither  pine  oil  nor  rosin  spirit  can  be  substituted  for  turpentine  in  the 
manufacture  of  artificial  camphor. 

Other  products  resembling  turpentine  find  their  way  into  com- 
mercial channels.     "Recovered  turpentine,"  a  name  sometimes  applied 
to  the  mixture  of  terpenes,  chiefly  i-limonene,  is  produced  by  decom- 
posing the  liquid  hydrochlorides  obtained  as   a.  by-product  in  the 
manufacture   of  bornyl   chloride   and   artificial   camphor.    Approxi- 
i  mately  90  per  cent  of  this  product  boils  within  the  range  170°-180°, 
i  depending  upon  the  rectification  and  purification  of  the  product.    The 
[presence  of  chlorides,  as  indicated  by  the  Beilstein  or  other  halogen 
I  tests,  is  indicative  of  such  an  origin.    The  oils  given  off  during  the 

« Cf.  Frankforter,  J.  Am.  Chem.  Soc.  28,  1467    (1906)  ;   Hawley  &  Palmer,  U.   S. 
.Forest  Service  Bull.  109  (1912)  ;  French  &  Withrow,  J.  Ind.  d  Eng.  Chem.  6,  148  (1914). 
*Teeple,  «/.  Am.  Chem.  Soc.  SO,  412   (1908). 


422       CHEMISTRY  OF  THE  NON-BENZEN01D  HYDROCARBONS 

melting  of  varnish  gums  are  sometimes  recovered  but,  even  after  good 
purification,  have  never  found  favor  as  thinners  with  paint  and  varnish 
manufacturers.  The  softer  grades  of  Manila  copal 5  yield  10  to  12  per 
cent  of  its  weight  of  oil,  largely  limonene  and  i-limonene,  during  the 
first  part  of  the  fusion,  up  to  about  330°.  Fresh  Queensland  Kauri 
gum,  from  Agathis  robusta,  yields  about  11.6  per  cent  of  nearly  pure 
a-pinene.6 

Parry 7  gives  the  following  physical  properties  of  turpentine  as 
the  result  of  the  examination  of  a  large  number  of  commercial  samples. 

Specific  gravity  at  15° 0.862-    0.870 

n        1.468-    1.473 

D 

Initial  boiling-point  154.°    -155.5° 

Distillate  below  160°  72.%  -  74.5% 

Distillate  below  170°   95.%  -  97.5% 

Iodine  value,  Hiibl   360.      -375. 

Iodine  value,  Wijs  335.      -350. 

The  optical  rotatory  power  is  subject  to  considerable  variation. 
Herty8  found  the  oil  from  P.  palustris  to  vary  from  — 7°  26'  to 
+  18°  18'  and  that  from  P.  heterophylla,  —  29°  26'  to  +  0°  15'. 

The  volatile  oils  of  several  species  of  pine  found  in  the  western 
States  have  been  examined  by  A.  W.  Schorger,9  who  finds  that  the 
turpentine  from  P.  Ponderosa  (Laws)  and  P.  Scopulorum  (Eng.)  con- 
sists largely  of  (3-pinene  (q.v.) :  that  from  P.  Sabiniana  is  practically 
pure  n. heptane  and  that  from  P.  contorta  consists  largely  of  (3-phel- 
landrene.  These  oils  are  not  likely  to  become  of  commercial  im- 
portance. 

Pinus  sylvestris  is  the  chief  source  of  Swedish  and  Russian  tur- 
pentine and  contains  sylvestrene  in  addition  to  dipentene  and 
(3-pinene  10  and  possibly  a-pinene  and  Z.eamphene.  Russian  turpen- 
tine is  a  very  indefinite  product  containing  considerable  proportions  of 
phenolic  or  acid  substances  and  oil  boiling  above  180°. 

French  oil  of  turpentine,  which  constitutes  nearly  20  per  cent  of 
the  world's  supply,  is  derived  from  Pinus  pinaster  (Pinus  maritima) 
and  is  a  true  pinene  turpentine  consisting  chiefly xl  of  Z.-a-pinene, 
[a]  —20°  to  —38°.  It  is  suitable  for  the  manufacture  of  artificial 

6  Brooks,  Philippine  J.  Sci.  1910,  203. 

•Baker  &  Smith,  "A  Research  on  the  Pines  of  Australia,"   Sydney,  1910,  p.  376. 

T  Chemistry  of  Essential  Oils,  Ed.  3,  Vol.  I,  17. 

8J.  Am.  Chem.  Soc.  30,  863   (1908). 

9  Bull.  119,  U.  S.  Dept.  Agriculture. 

10  Chem.  Ztff.  32,  8   (1908). 

"Darmois  (Chem.  Zentr.  1910  [1],  30)  concludes,  from  studies  on  its  optical  rota- 
tion, that  this  turpentine  consists  of  approximately  62%  a-pinene  and  38%  /3-pinene. 


BICYCLIC  NON-BENZENOID  HYDROCARBONS  423 

camphor  or  other  uses  to  which  a  true  pinene  oil  can  be  put.  With 
this  brief  review  of  the  character  of  commercial  turpentines  the  chem- 
istry of  the  pinenes  and  their  more  important  derivatives  will  be 
noted.  With  the  elucidation  of  the  constitution  of  (3-pinene  and  its 
synthesis  by  Wallach  in  1908,  the  chemistry  of  the  pinenes  is  prac- 
tically complete. 

a-Pinene  is  one  of  the  most  widely  distributed  of  the  terpenes, 
having  been  found  in  the  essential  oils  of  a  large  number  of  Coniferse, 
the  grass  oils,  Lauraceae,  Labiatae,  etc. 

When  it  occurs  together  with  other  terpenes  in  oils  used  for  the 
manufacture  of  flavoring  extracts  or  perfumes,  it  is  common  practice 
to  separate  the  terpenes  by  making  use  of  their  lesser  solubility  in 
dilute  alcohol,12  as  compared  with  the  esters,  alcohols,  aldehydes  and 
the  like  which  give  such  oils  their  aromatic  value.  The  resulting  ter- 
pene-free  oils  can  be  dissolved  in  much  more  dilute  alcohol,  thereby 
effecting  considerable  saving  in  the  preparation  of  these  solutions. 

Inactive  a-pinene  is  one  of  the  few  terpenes  which  have  been  iso- 
lated in  quite  a  pure  condition.  Fairly  pure  a-pinene  can  be  obtained 
by  fractional  distillation  of  turpentine 13  but  a  purer  product  can  be 
obtained  by  preparing  the  nitrosochloride,  purifying  this  by  fractional 
crystallization  and  regenerating  the  a-pinene  by  decomposing  the 
nitrosochloride  by  aniline 14  in  alcoholic  solution.  Such  a  sample 
described  by  Schimmel  &  Co.15  had  the  following  physical  properties: 

20° 

boiling-point  154.5°-155°,  d1  _0  0.8634,  n_-1.4664,  optically  inactive. 

lo  D 

The  highest  observed  optical  rotations  of  a-pinene  are  [«]n  +  51.52° 

in  the  case  of  pinene  isolated  by  A.  W.  Schorger 16  from  the  oil  of  the 
Port  Orford  cedar  (Chamcecyparis  lawsoniana).  This  is  probably  the 
purest  natural  a-pinene  thus  far  discovered.  A  very  pure  d.  a-pinene 
[aU  +  48.4°  has  been  noted  in  the  case  of  a  specimen  isolated  from 

Greek  turpentine  (from  the  Aleppo  pine,  P.  halepensis)  ,17  and  a  laevo- 
pinene  [a]  — 48.63°  from  one  of  the  eucalyptus  oils,  E.  lavopinea.1* 

12  Bocker,  J.   prakt.  CTiem.    (2)   89,  199    (1914)  ;  Vezes  &  Mouline,  Bull.  soc.  cMm. 
(3)  31,  1043   (1904).     See  section  on  physical  properties   (solubility). 

13  Henderson  &  Sutherland  recommend  fractional  distillation  with  steam,  followed 
by    ordinary   distillation,    taking   the    fraction    boiling    at    155°-156°    as    a-oinene.      (J. 
Chem.  Soc.  101,  2289   [1912]). 

"Wallach,  Ann.  258,  343   (1890). 

35  Gildemeister,  "Die  Aetherischen  Oele,"  Ed.  2,  Vol.  1,  308. 

16  J.  Ind.  &  Eng.   Chem.  6,  631    (1914). 

"Vezes,   Bull.   soc.  chim.    (4»    5,   932    (1909). 

"Smith,  J.  d  Proc.  Soc.  X.  8.   W.  32,  195    (1898). 


424       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


Oils  of  high  optical  rotation  give  very  poor  yields  of  crystalline  nitro- 
sochloride. 

a-Pinene  is  usually  identified  by  preparing  the  nitrosochloride  of 
the  fraction  boiling  below  160°,  which  preparation  is  carried  out  by 
slowly  adding  concentrated  hydrochloric  acid  to  a  strongly  cooled 
solution  of  the  hydrocarbon  in  glacial  acetic  acid  and  ethyl  or  amyl 
nitrite.  On  standing  the  crystalline  nitrosochloride  separates.  After 
separating  the  crystals  and  recrystallization  by  dissolving  in  chloro- 
form and  precipitating  with  methyl  alcohol,  the  nitrosochloride  melts 
at  103°  but  the  nitrolamines  give  melting-points  which  are  more  use- 
ful and  reliable  for  identification  purposes.  The  pinene  nitrolpiperi- 
dine  melts  at  118°-119°  and  the  nitrobenzylamine  melts  at  122°-123°. 
In  preparing  the  nitrolpiperidine  a  small  proportion  of  nitrosopinene  is 
simultaneously  formed.19  In  the  case  of  pinene  of  high  optical 
activity  recourse  may  be  had  to  oxidation  by  permanganate  to  the 
pinonic  acids.20  The  hydrochloride  (bornyl  chloride)  made  by  pass- 
ing dry  hydrogen  chloride  into  cooled  pinene,  carefully  dried  by  dis- 
tillation over  sodium,  has  also  been  employed  for  the  detection  of 
pinene  although  both  a  and  p-pinenes  give  the  same  hydrochloride, 
melting-point  127°. 

The  constitution  of  a-pinene  has  been  determined  largely  by  a 
study  of  its  oxidation  products.  One  of  the  most  important  advances 
made  in  clearing  up  the  chemistry  of  the  terpenes  was  the  recognition, 
first  clearly  set  forth  by  Wagner,  that  the  hydroxyl  group  in  a-terpi- 
neol  is  in  position  (8)  and  not  position  (4) .  In  this  same  remarkable 
communication  of  Wagner,21  which  was  published  in  full  in  the  Rus- 


a-pinene  (Wagner) 


H 

+  H.O    H 

r 

H, 

^ 

H 

Ss-r 

Ha 

r 

Jc.—  OH 

er) 

^X^          X. 

CH^  XCH, 

"Wallach,  Ann.  2tft  252    (1888).     Confirmed  by  Bushujew,  J.  Rusa.  Phya.-Chcm. 
800.  41,  1481    (1910). 

a°Schimmel  &  Co.  Semi-Ann.  Rep.  1909  (1),  120. 
aiBer.  27,  2270    (1894). 


BIG YC LIC  NON-BENZENOID  HYDROCARBONS 


425 


sian  language,  Wagner  published  what  have  proven  to  be  the  correct 
constitutions  of  limonene,  carvone,  dihydrocarvone,  carone  and 
a-pinene.  According  to  Wagner's  structure  for  ct-pinene,  the  forma- 
tion of  cc-terpineol  and  terpin  is  formulated  as  shown  on  the  preced- 
ing page.  Wagner  seemed  to  have  an  almost  uncanny  ability  to 
visualize  the  constitution  of  such  substances. 

Baeyer  showed  that  a  series  of  oxidation  products  obtained  by  him 
also  are  in  accord  with  Wagner's  a-pinene  constitution,  which  oxida- 
tions he  expressed  as  follows,22 


a-pinene 


a-pinonic  acid          pinoylformic  acid 


CO,H 


Hqc 

pinic  add  norpinic  acid23 


Just  as  the  four  carbon  ring  in  pinene  is  broken  by  dilute  acids  to 
form  terpineol,  so  also  is  the  four  carbon  ring  in  a-pinonic  acid  broken 
to  give  the  methyl  ketone  of  homoterpenylic  acid,  identical  with  the 
product  of  the  oxidation  of  terpineol  itself.  (See  page  426.) 

a-Pinene  is  usually  associated  with  the  isomeric  hydrocarbon, 
|3-pinene,  and  oxidation  by  permanganate  gives  the  products  of  oxida- 

2*Ber.  W,  2775    (1896). 

23  The  cyclobutane  ring  has  about  equal  stability  in  pinene,  pinonic  acid  and 
pinoylformic  acid,  being  split  with  about  equal  ease  by  dilute  acids.  In  pinic  and 
norpinic  acid  it  is  very  much  more  stable,  this  stablity  being  due  apparently  to  the 
influence  of  the  carboxyl  group,  parallel  to  the  observations  of  Buchner  on  the  effect 
of  the  carboxyl  group  on  the  stability  of  the  cyclopropane  ring. 


426       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

c/' 

HO.C 


a-pinonic  acid 

,8, 


CM,' 

methyl  ketone  of 

^  homoterpenylic  acid 

HQ; 

ci 

a-terpineol 

tion  characteristic  of  these  two  hydrocarbons.  The  oxidation  is  car- 
ried out25  as  follows:  5  cc.  of  the  hydrocarbon  are  shaken  for  about 
three  hours  with  an  ice  -cold  solution  of  12  g.  potassium  permanganate, 
2.5  g.  caustic  soda,  200  cc.  of  water  and  500  g.  ice.  After  3  hours 
saturate  with  carbon  dioxide  and  remove  the  volatile  unoxidized  oil 
by  distillation  with  steam,  filter  and  evaporate  in  a  current  of  carbon 
dioxide  to  about  200  cc.  and  extract  several  times  with  chloroform.  On 
further  evaporation  the  first  salt  to  separate  out  is  sodium  nopinate, 
which  on  acidifying  gives  crystalline  nopinic  acid,  melting  at  125°. 
This  acid  is  characteristic  for  |3-pinene.  The  sodium  salt  of  pinonic 
acid  is  more  soluble  than  the  nopinate.  Barbier  and  Grignard  26  have 
investigated  the  optically  active  forms  of  pinonic  acid  obtained  by 
the  oxidation  of  d.  and  Z.a-pinene  of  high  optical  rotation.  From 
Z.pinene,  [a]  —  37.2°  Lpinonic  acid  was  obtained,  by  permanganate 

oxidation  and  after  distillation  in  vacuo,  189°-195°  at  18  mm.,  sepa- 
rated in  long  crystals  melting  at  67°-69°,  and  [a]  —90.5°.  From 

24  The  constitution  of  homoterpenylic  and  terpenylic  acids  is  discussed  in  connec- 
tion with  terpineol  and  limonene. 

"Schimmel  &  Co.  Semi- Ann.  Rep.  1910   (1),  165. 
"Compt.  rend,  lift,  597   (1908). 


BICYCLIC  NON-BENZENOID  HYDROCARBONS  427 

d.a-pinene,   [«]n  +  39.4°,  they  obtained  a  mixture  of  racemic  and 

dpinonic  acids,  the  latter  melting  when  recrystallized  at  67°-68°, 
[a]n  +  89.0°  and  when  mixed  with  the  i.pinonic  acid  the  racemic 

acid  melting  at  104°  was  obtained. 

Harries 27  investigated  the  action  of  ozone  on  a-pinene  and  by 
heating  the  resulting  ozonide  with  acetic  acid  to  90°  obtained  an  oil 
boiling  over  the  wide  range  of  100°-142°  under  12  mm.,  from  which  he 
prepared  a  semicarbazone  melting  at  214°-215°  which  was  "prob- 
ably" pinonic  aldehyde.  On  standing  in  contact  with  moist  air,  as 
in  loosely  stoppered  containers,  particularly  in  sunlight,  turpentine  or 
a-pinene  is  oxidized  to  pinol  hydrate  (sobrerol)  which  crystallizes 
from  the  oil.28  From  d.  or  ^.turpentine  the  correspondingly  active 
pinol  hydrates,  melting-point  150°,  are  obtained.  The  d-l  hydrate  is 
formed  on  treating  pinol  with  hydrogen  bromide  followed  by  hydrol- 
ysis by  alkali.  The  relations  of  pinol  hydrate  and  pinol  are  indicated 
by  the  results  on  oxidizing  with  permanganate.  Each  adds  two 
hydroxyl  groups,  pinol  to  form  pinol  glycol,  C10H160.  (OH)2  and  the 
hydrate  to  form  sobrerythrite 29  C10H16(OH)4.  Pinol  glycol  is  also 
formed  by  the  action  of  dilute  acids  on  the  dioxide,  pinol  oxide, 
C10H1602.  Sobrerythrite  is  also  formed  by  the  action  of  hypochlorous 
acid  on  pinene  and  hydrolysis  of  the  dichlorohydrin.  In  accord  with 
the  general  behavior  of  the  higher  alkylene  oxides  (q.v.)  concentrated 
alkalies  convert  the  dichlorohydrin  to  the  dioxide,  pinol  oxide,  and  on 
treating  pinol  oxide  with  dilute  acids  the  1.2  oxide  is  hydrolyzed  to 
pinol  glycol,  leaving  the  oxide  ring  of  four  carbon  atoms  unchanged. 
Parallel  with  the  behavior  described  in  connection  with  cineol  and 
other  oxides,  heating  pinol  hydrate  with  dilute  acids  causes  the  /or- 
mation  of  the  oxide  pinol.  These  facts  show  clearly  the  relation  be- 
tween the  number  of  carbon  atoms  in  the  oxide  ring  and  their  relative 
stability.  (See  figure  on  page  428.) 

The  behavior  of  turpentine  or  pinene  on  air  oxidation  is,  in  gen- 
eral, typical  of  the  behavior  of  the  olefines,  including  unsaturated 
petroleum  oils.  With  all  such  substances  air  oxidation  is  accom- 

"  Ber.  tf,  879   (1909). 

28  Formic  acid  is  one  of  the  products  of  the  oxidation  of  turpentine  by  air  and 
metal  containers  are  accordingly  sometimes  corroded  by  old  turpentine.     Formic  acid 
produced  in  this  way  is  probably  a  product  of  the  oxidation  of  /3-pinene,  not  o-pinene. 

29  The   sobrerythrite   made   from    pinol    hydrate    melts    at    156°  ;    a    stereoisomeric 
sobrerythrite  made  by  the  action  of  hypochlorous  acid  on  pinene  melts  at  194°. 


428       CHEMISTRY  OF  THE  NON-BENZENO1D  HYDROCARBONS 

CH,  CH, 


pmol  oxide 


binol  olycol 


P1 


not 


panied  by  the  formation  of  organic  peroxides,  water,  carbon  dioxide, 
simple  organic  acids,  resinous  substances  and  other  oxidation  products 
among  which  alcohols,  aldehydes  and  ketones  have  frequently  been 
noted.  The  oxidizing  power  of  old  turpentine  was  observed  by  Schon- 
bein  and  frequently  investigated  subsequently  by  others.  The  organic 
peroxides  formed  in  this  way  are  rapidly  destroyed  by  heating  to  140° 
and  are  hydrolyzed  by  water.  As  pointed  out  by  Engler  and  Weiss- 
berg81  the  peroxides  decompose,  causing  further  oxidation  of  other 

80  The  positions  of  the  chlorine  atoms  and  hydroxyl  groups  may  be  reversed  ;  in  the 
above  constitution  their  positions  are  arbitrarily  assigned.  The  dichlorohydrine  of 
pinene  may  be  a  mixture  of  isomers,  just  as  the  addition  of  HOC!  fo  propylene  gives 
a  mixture  of  CH8CHC1.CH2OH  and  CH3CHOH.CH,C1. 

M  Vorgange  <Jer  Autoxidation,  1904, 


I 

BICYCLIC  NON-BENZENOID  HYDROCARBONS  429 

material  32  or  unchanged  oil  or  may  even  decompose  breaking  up  the 
pinene  molecule  ;  the  formation  of  peroxides  cannot  be  observed  above 
160°  although  very  rapid  oxidation  by  air  occurs  at  this  temperature. 
It  is  well  known  that  old  oxidized  turpentine  "dries"  more  rapidly 
than  freshly  distilled  turpentine  and  it  is  also  a  fact  very  generally 
observed  that  air  oxidation  greatly  promotes  resinification.  Krumb- 
haar33  noted  that  a  sample  of  oil  containing  0.002  g.  active  oxygen 
per  cubic  centimeter  of  turpentine  "dried"  very  much  faster  than  one 
containing  0.00057  g.  active  oxygen.3*  Among  the  products  of  the 
oxidation  of  turpentine  by  moist  air  in  iron  vessels  is  verbenone  and 
the  corresponding  alcohol  verbenol.  From  Grecian  turpentine  d.  ver- 
benone was  obtained  and  from  French  turpentine  Z.verbenone  and 
dverbenol.35  By  the  oxidation  of  pinene  by  benzoyl  peroxide,  an 
oxide  is  produced  boiling  at  102°-103°  (50  mm.)  which  yields  pinol 
hydrate  on  hydrolysis.36  On  oxidizing  with  hydrogen  peroxide37  or 
mercuric  acetate  the  four-carbon  ring  is  broken;  the  chief  product  of 
the  action  of  hydrogen  peroxide  on  pinene  (by  30  per  cent  hydrogen 
peroxide  and  glacial  acetic  acid)  is  a-terpineol.  Small  proportions  of 
borneol,  a  little  menthane-1.4.8-triol  and  resinous  material  are  also 
formed.  The  expected  pineneglycol  was  not  found.  Oxidation  by 
mercuric  acetate  gave  pinol  hydrate.38 

By  hydrogenating  a-pinene  in  the  presence  of  reduced  nickel 
Sabatier39  obtained  pinane,  boiling-point  166°,  and  in  the  presence 
of  catalytic  copper  an  impure  pinane,  boiling  at  163°-170°,  results.40 
Skita,41  using  platinum  black,  evidently  did  not  get  pure  pinane,  but 
Vavon42  reports  a  quantitative  yield  of  pinane,  boiling-point  166° 
(755mm.),  [a]D  +  22.7°  from  d.pinene  or  —21.3°  for  Z.pinane  from 

15° 

l.pinene  from  French  turpentine,  d  —  -  0.861,  and  solidifying-point 

15 

about  —  45°.    Boeseken  43  used  pinene  and  platinum  black  in  Study- 

's Sieburg  (Biochem.  Zt.  tf,  280  [1913]),  investigating  the  reputed  efficacy  of 
oxidized  turpentine  as  an  antidote  for  yellow  phosphorus  poisoning  found  that  a  com- 
pound of  pinene  and  "phosphorous  or  hypophosphorous  acid"  was  formed,  but  Will- 
eo  and  Sonnenfeld,  Ber.  p,  3172  (1914),  isolated  a  yellow  crystalline  compound, 
f  Qt  Pinene  and  yellow  Phosphorus  with  dry  air. 


"Determined  by  Klasson's  method,  Chem.  Als.  5,  3345. 
35Blumann  &  Zeitschel,  Ber.  46,  1178   (1913). 
86  Prileschajew,   Ber.  42,   4811    (1909). 

Henderson  &  Sutherland,  J.  Chem.  Soc.  101,  2288  (1912) 
"Henderson  &  Agnew,  J.  Chem.  Soc.  95,  285   (1909). 
88  Compt.  rend.  132,  1254   (1901). 


«°Ipatiev,  Ber.  43,  3546  (1910). 
41  Ber.  45,  3585    (1912). 
«  Compt.  rend.  1^9,  997   (1909). 
43  Rec.  trav.  chim.  35,  288  (1916). 


430      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

ing  the  effect  of  solvents  on  the  rate  of  hydrogenation;  in  formic  acid 
and  in  ethyl  alcohol  the  hydrogenation  is  very  slow  and  the  catalyst 
becomes  poisoned.  Glacial  acetic  acid,  as  recommended  by  Will- 
statter,  was  most  satisfactory.  When  using  this  solvent  cyclopropane 
is  slowly  reduced  to  propane  but  under  the  same  conditions  the  cyclo- 
butane  ring  in  pinene  is  not  attacked.  During  the  war  Sabatier, 
Mailhe  and  Gaudion44  investigated  the  decomposition  of  pinene  at 
high  temperatures  in  the  presence  of  various  metallic  catalysts. 
Large  scale  experiments  on  several  tons  of  turpentine,  using  catalytic 
copper  at  550°,  gave  about  21  per  cent  of  hydrocarbons  capable  of 
being  nitrated.  No  dehydrogenation  was  observed  at  350°.  At  600° 
to  630°  in  the  presence  of  copper  the  decomposition  was  extensive, 
forming  considerable  gas  and  a  mixture  of  hydrocarbons  boiling  from 
30°  upwards  and  containing  butylenes,  amylenes,  isoprene,  hexylenes, 
aromatic  hydrocarbons,  etc.,  the  mixture  closely  resembling  the  prod- 
ucts resulting  from  the  decomposition  of  petroleum  oils  under  these 
conditions,  or  the  light  liquid  condensed  from  Pintsch  gas.  Also  as 
in  the  case  of  petroleum  hydrocarbons,  passing  turpentine  over  nickel 
at  600°  gave  rapid  deposition  of  carbon  and  much  gas  rich  in  hydro- 
gen until  the  catalyst  was  rendered  inoperative  by  the  deposited 
carbon. 

As  noted  above,  in  connection  with  the  identification  of  a-pinene, 
pinenes  of  very  high  optical  activity  give  no  crystalline  nitrosochloride 
when  the  usual  method  of  preparation  is  followed,  and  Kremers 45 
showed  that  the  yield  of  the  nitrosochloride  varied  inversely  as  the 
rotation  although  the  yield  almost  never  exceeds  40  per  cent  of  the 
theory.  The  crystalline  nitrosochloride  obtained  is  optically  inactive 
and  although  a  crystalline  product  can  be  obtained  by  first  mixing 
strongly  d.  and  Lpinenes,  no  crystalline  product  can  be  obtained  by 
mixing  the  nitrosochloride  solutions  obtained  by  separately  treating 
strongly  rotatory  d.  and  Lpinenes.46  Tilden  investigated  the  matter 
and  concluded  that  the  poor  yield  from  pinene  of  high  rotation  is  due 
to  the  destructive  effects  of  the  heat  internally  or  locally  generated  in 
the  reaction  mixture.47  Lynn48  has  recently  succeeded  in  preparing 
optically  active  a-pinene  nitrosochloride  from  the  highly  rotatory 

"Compt.  rend.  168,  926   (1919). 

wProc.  Wise.  Pharm.  Assoc.  1892,  66. 

«  Gildemeister  &  Kohler,    Wallach  Festschr.  1909,  432. 

«J.  Chem.  Soc.  85,  759   (1904). 

48  J.  Am.  Chem.  Soc.  1,1,  361  (1919).  For  this  purpose  Lynn  modified  the  usual 
method  for  preparing  nitrosochlorides,  using  ethyl  nitrite,  absolute  alcohol  and  alcoholic 
hydrogen  chloride,  the  acid  not  being  in  excess. 


BICYCLIC  NON-BENZENOID  HYDROCARBONS 


431 


d.a-pinene  from  the  Port  Orford  cedar,  previously  described  by 
Schorger,  and  also  regenerated  d.a-pinene  from  this  nitrosochloride 
having  a  rotation  of  [a]n  +  53.75°  (in  4  per  cent  alcoholic  solution) 

which  is  the  highest  value  yet  reported  and  agrees  well  with  the  high 
value,  +  51.52°,  previously  reported  by  Schorger  for  the  natural 
pinene  from  this  cedar.  The  active  nitrosochloride,  [ct]n  -f-  322°, 

melts  at  81°-81.5°,  and  is  markedly  soluble  in  all  the  common  sol- 
vents, which  probably  accounts  for  the  fact  that  it  was  not  discovered 
earlier.  The  d.nitrolbenzylamine  melts  at  144°-145°  and  the  nitrol- 
piperidine  at  84°.  Nevertheless,  to  account  for  the  low  yields  of 
nitrosochloride  Lynn  suggests  that  the  four-carbon  ring  may  be  broken 
to  give  6-nitroso-8-chloro-A1-p-menthene,  or  may  react  to  give  a 
product  C10H15NO  +  HC1  in  a  manner  similar  to  the  reaction  of 
nitrosyl  chloride  on  n.heptane.49 

When  pinene  nitrosochloride  is  treated  with  sodium  methoxide, 
a  methyl  ether  derivative  is  formed,50  melting-point  102°,  whose 
chemical  behavior  indicates  the  constitution, 


Ci 


HON. 


However,  the  chief  result  of  the  action  of  alcoholic  caustic  alkali  on 
pinene  nitrosochloride  is  the  elimination  of  HC1  in  the  usual  way  to 
form  nitrosopinene, 

:n3  ^  CH, 


WON 


a-pinene  nitrosochloride     nitrosopinene,  M.-P.  130°-131° 

*  Lynn,  J.  Am.  Chem.  Soc.  41,  367   (1919),  finds  that  n. heptane  reacts  with  NOC1 
in  sunlight  to  give  HC1.  ammonium  chloride  and  a  mixture  of  heptanones. 
^Deussen  &  Philipp,  Ann.  369,  62   (1909)  ;  374,  112   (1910). 


432      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


By  warming  with  aqueous  oxalic  acid  the  oxime  group  is  hydrolyzed 
to  the  ketone,  carvopinone,51  but  in  acetic  acid  solution  with  oxalic  or 
hydrochloric  acids  the  four-carbon  ring  is  broken  forming  carvone. 

CH. 


HONN 


carvopinone 


by  dilute  acids 


carvone 


By  reduction  with  zinc  dust  and  acetic  acid  nitrosopinene  yields  the 
unsaturated  amine,  pinylamine  52  and  a  saturated  ketone,  pinocam- 
phone 53  CH, 

I        •? 


CK 


HON 


pinylamine 


pinocamphone 


"Wallach,  Ann.  $46,  231   (1906)  ;  boiling-point  94°-96°   (12mm.),  readily  converted 
to  carvone  by  heating  witb  dilute  acids. 

"Wallach,   loc.  cit. ;  Pinylamine  boils  at  207°-208°,  d15o    0.944.     The  nitrate  1* 

sparingly  soluble  in  water  which  can  be  used  for  its  recrystallization.   The  hydrochloride, 
melting-point  229°-230°,  decomposes  on  heating  to  give  ammonium  chloride  and  cymene. 
»  Wallach,  Stf,  235   (1906)  ;  360,  92   (1908)  ;  S89t  185   (1912).     The  yield  of  pino- 
camphone by  the  reduction  of  nitrosopinene  is  about  22%.     It  boils  at  211°-213°  and 


BICYCLIC  NON-BENZENOID  HYDROCARBONS 


433 


The  first  application  of  the  method  of  exhaustive  methylation  of 
amines  and  their  subsequent  decomposition,  which  has  been  exceed- 
ingly useful  in  the  study  of  the  constitution  of  alkaloids,  to  the  prepa- 
ration of  terpenes  is  the  recent  work  of  Ruzicka."  On  hydrogenating 
pinylamine  the  saturated  amine  pinocamphylamine  is  formed,  which 
on  exhaustive  methylation  gives  the  trimethylpinocamphyl-ammo- 
nium  hydroxide,  the  decomposition  of  which  yields  pure  a-pinene,  as 
follows, 

H, 

LI 


pinylamine          pinocamphylamine        trimethyl 


a-pinene 


It  is  of  interest  to  note  that  the  four-carbon  ring  in  pinocamphone  is 
very  much  more  stable  to  acids  than  the  unsaturated  ketone,  carvo- 
pinone.  The  same  stability  is  noted  in  the  corresponding  alcohol, 
pinocampheol,55  made  by  the  reduction  of  pinocamphone. 

In  general  the  halogen  of  alkyl  halides  56  may  be  substituted  by 

N 
the  triazo  group,  — N<||  .    When  a-pinene  nitrosochloride  is  treated 

.N 
in  alcoholic  solution,  with  sodium  azide,  reaction  takes  place  at  about 

40°  to  give  a  beautifully  crystalline  pinenenitrosoazide  melting  at 
120°.  Sodium  ethoxide  decomposes  the  azide  to  nitrosopinene.  The 
chemical  behavior  of  pinenenitrosoazide,  and  its  physiological  effect, 
is  that  of  the  aliphatic  triazo  derivatives  in  general.  By  heating  with 
water  the  azide  melting  at  120°  is  partially  isomerized  to  an  azide 
melting  at  126°  and  hot  water  alone  breaks  the  four-carbon  ring  in 
the  latter  azide,  losing  nitrogen  also,  to  form  hydroxydihydrocarvox- 
ime.57 

has  a  density  of  0.959  (20).  It  yields  an  oxime  melting  at  868-87°  and  a  semlcar- 
bazone  melting-point  208°.  On  oxidation  it  gives  a-pinonic  acid  and  an  isomeric  cam- 
phoric acid,  Ci0H16O4,  melting  at  186°-187°. 

"Ruzicka  &  Trebler,  Helv.  Chim.  Acta.  S,  756  (1920). 

"Wallach,  Ann.  389,  188   (1912). 

M  Thus  ethylenechlorohydrin  reacts  with  NaN8  to  give  triazoethyl  alcohol.  Vinyl 
bromide,  which  does  not  react  with  sodium  azide,  is  an  exception,  which  is  another 
illustration  of  the  stabilizing  effect  of  an  adjacent  double  bond  upon  a  halogen  atom. 

"Forster  &  Newman,  J.  Chem.  Soc.  99t  245   (1911). 


434      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


HON; 


H          HON= 


nitrosoazide,  M.-P.  120°    nitrosoazide,  M.-P.  126( 


When  a  solution  of  ethyl  diazoacetate  in  a  little  d.Z.a-pinene  is 
slowly  added  to  a  mixture  of  the  pinene  and  copper  powder  at  160°- 
165°,  nitrogen  is  vigorously  evolved  and  the  resulting  ester  can  be 
oxidized,  through  several  intermediate  products,  to  methylcyclopro- 
pane  -1.2.3.-tricarboxylic  acid.  Buchner,58  who  has  also  applied 
this  method  to  the  study  of  the  constitution  of  camphene  and  bor- 
nylene,  considers  that  the  results  are  best  interpreted  by  Wagner's 
formula  for  a-pinene. 


tricyclooctane 
derivative 


methylcyclopropane- 

1 .2.3.-carboxylic 

acid 


Bromine  reacts  energetically  with  a-pinene  in  cooled,  dry  carbon 
bisulfide  to  give  a  dibromide  (reaction  proceeds  further  with  excess 
bromine,  HBr  being  simultaneously  evolved).  When  the  crude  di- 
bromide is  distilled  with  steam  considerable  decomposition  occurs  but 
one  of  the  products  is  a  crystalline  dibromide,  C10H16Br2,  of  unknown 
constitution  but  which  probably  belongs  to  the  camphor  series.59 

Verbenone:  This  ketone  derivative  of  pinene  was  discovered  in  the 


68  Ser.  $,  2680    (1913).     The  trimethyltricyclooctanecarboxylic  acid,  noted  above, 
melts  at  165°. 

"Wagner  &  Ginsberg,  Ber.  C9,  890   (1896). 


BICYCLIC  NON-BENZENOID  HYDROCARBONS 


435 


essential  oil  of  verbena  60  and  has  more  recently  been  investigated  by 
Blumann  and  Zeitschel,  who  found  it  in  turpentine  which  had  been 
considerably  oxidized  by  the  air.61  It  has  a  camphor  and  mint-like 
odor  and  its  constitution  was  shown  (by  oxidation  to  pinononic  acid, 
and  other  properties)  to  be  as  follows: 


CH3 


=  C 


CH 


CH3 


V 


CH2 


H02C 


verbenone 


CH, 


\ 

H 

pinononic  acid 


CH2 


The  fact  that  the  double  bond  in  pinene  should  apparently  be  pre- 
served, may  be  explained  by  the  initial  hydration  of  the  double  bond, 
then  oxidation  of  the  CH2  group  and  subsequent  splitting  off  of  water 
to  form  a  double  bond  in  the  original  position.  Catalytic  hydrogena- 
tion,  using  colloidal  palladium,  yields  the  saturated  ketone,  dihydro- 
verbenone,62  isomeric  with  pinocamphone. 

The  corresponding  alcohol,  verbenol,™  also  occurs  in  turpentine 
oxidized  by  air.  The  alcohol  readily  composes  when  distilled  or  when 
heated  with  acetic  anhydride,  forming  verbenene,  C10H14,  which 

•°  Kerschbaum,  Ber.  S3,  885    (1900). 

"Ber,  tf,  1178  (1913).  Verbenone  boila  at  227°-228°,  or  100°  at  16mm.  melts  at 
6.5,  has  a  density  of  0.9780  at  15°  and  [a]D  -f-  249.62°.  Its  oxime  melts  at  115°. 

« Dihydro-d.verbenone,  Ci0H10O,  is  an  oil  boiling  at  222°,  d15<,  0.9685,  semicar- 
bazone  melting  at  220°-221°  and  oxime  at  77°-78°. 

•»  Boiling-point  216°-218'.  d15<>   0.9742. 


436       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

hydrocarbon  probably  has  two  double  bonds  in  a  conjugated  position 
as  in  a-terpinene.  Dehydration  of  verbenol  with  phosphoric  oxide  or 
zinc  chloride  gave  cymene.  When  /.verbenene,  prepared  from  ver- 
benol, is  brominated  in  chloroform  the  crystalline  dibromide,  melt- 
ing at  70°-72°,  is  formed.  The  d.dibromide  from  d  verbenene  nat- 
urally melts  at  the  same  temperature  but  the  racemic  dibromide  melts 
at  50°-52°.  Oxidation  of  verbenene  by  permanganate  yields  norpinic 
acid  melting  at  1 75.5 °-l 76.5°,  and  treatment  with  zinc  chloride  yields 
p-cymene.  Blumann  and  Zeitschel 64  regard  verbenene  as  having  the 
constitution  shown  below,  I;  on  reduction  by  sodium  and  alcohol  two 
atoms  of  hydrogen  are  added  (a  reduction  usually  possible  when  the 
double  bonds  are  conjugated)  and  the  resulting  hydrocarbon,  dihydro- 
verbenene  or  "S-pinene"  they  regard  as  having  the  constitution  indi- 
cated by  II. 


/.  verbenene 


0.8867 


II.  dihydroverbenenef 
B.-P 158°-159°  (762  mm.) 


20 


n-p- 1.4980 

B.-P 159M60' 

"Ber.  5k,  887   (1921). 


20 


0.8625 
1.4662 


BIG YC LIC  NON-BENZENOID  HYDROCARBONS 

CH, 


437 


verbenol 


verbenene  f 


An  alcohol  isomeric  with  verbenol  and  also  possessing  the  bridged 
ring  structure  of  pinene,  is  myrtenol,  an  alcohol  occurring  in  myrtle 
oil  as  the  acetate.65  Its  constitution  is  shown  by  the  fact  that  reduc- 
tion of  the  corresponding  chloride  by  sodium  and  alcohol  yields 


a-pmene 


66 


Oxidation  by  chromic  acid  yields  the  corresponding  aldehyde  myr- 
tenal,  but  permanganate  oxidizes  it  to  d.pinic  acid. 

The  conversion  of  pinene  to  derivatives  of  borneol  is  well  known, 
the  best  example  being  the  formation  of  bornyl  chloride  (so-called 
pinene  hydrochloride)  by  the  action  of  dry  hydrogen  chloride  on 


"Soden  &  Elze,  Chem.  Ztg.  29,  1031    (1905). 

«•  Semmler  &  Bartelt,  Ber.  W,  1363  (1907)  ;  myrtenol  boils  at  222°-224'   (760mm.) 
or  102°-105°   (9mm.). 


438       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


pinene  at  about  15°.    When  bornyl  chloride  is  prepared  from  pinene 
in  the  usual  manner,  the  product  is  usually  optically  inactive  but 


Barbier  and  Grignard  67  noted  a  rotation  of 


. 


—  25.20°  for  the 


hydrochloride,  melting-point  127°,  made  from  L-a-pinene  from 
French  turpentine,  and  a  d.pinene  hydrochloride  (bornyl  chloride), 
[a]  +  33.19°,  melting-point  127.1°,  has  been  prepared68  from  d.a- 

pinene  from  Greek  turpentine.  The  hydrochloride  made  by  Lynn 
from  highly  active  da-pinene  from  the  Port  Orford  cedar  was  inac- 
tive, from  which  observations,  together  with  many  other  observations 
of  similar  kind,  it  is  evident  that  racemization  occurs  very  readily, 
but  under  certain  conditions,  efficiency  of  cooling  or  rate  of  reaction, 
the  activity  may  be  partially  preserved.  In  preparing  limonene  mono- 
hydrochloride  partial  racemization  occurs,  the  degree  of  racemization 
apparently  being  influenced  by  the  rate  of  introducing  the  hydrogen 
chloride,  as  shown  by  Vavon.69  Pinene  hydroiodide  (bornyl  iodide) 
was  made  by  Aschan70  by  digesting  bornyl  chloride  in  ether  with 
magnesium  iodide;  the  iodide  is  easily  reduced  by  zinc  in  acetic  acid 
to  camphane. 

True  pinene  hydrochloride  has  not  been  detected  among  the  reac- 
tion products  of  a-pinene  and  hydrogen  chloride,  but  was  synthesized 
by  Wallach  from  nopinone  by  the  Grignard  reaction,  thus  making 
niethymopinol,  and  replacing  the  hydroxyl  group  in  this  alcohol  by 
chlorine  by  means  of  phosphorus  pentachloride,71 


nopinone 


methyl  nopinol 


pinene 
hydrochloride 


"Bull,  soc.  chim.    (4)   15/26    (1914). 

"Tsakalotos,  J.  pharm.  chim.  1J,,  97    (1916). 

99  Bull.  soc.  chim.    (4)    15,  282    (1914). 

70  Ber.  1,5,  2395  (1912)  ;  d.  or  Z.pinene  gives  a  hydroiodide  melting  at  — 3°  to  — 5"  ; 
d.l.pinene  gives  the  racemic  hydroiodide  melting  at  —  12°.  Silver  oxide  in  dilute  alcohol 
conyertsothe  iodide  into  an  evidently  new  unaaturated  alcohol,  CioH17OH,  boiling-point 

»l  Wallach,  Ann.  356,  246   (1907). 


BICYCLIC  NON-BENZENOID  HYDROCARBONS  439 

True  pinene  hydrochloride,  as  contrasted  with  bornyl  chloride,  is 
very  unstable  and  decomposes  at  its  boiling-point,  200°-205°,  and 
is  very  readily  converted  to  dipentene  dihydrochloride  by  the  action 
of  hydrogen  chloride ;  bornyl  chloride  is  not  affected  by  hydrogen 
chloride.  By  treating  pinene  dibromide  with  zinc  in  alcoholic  solu- 
tion a  tricyclic  hydrocarbon,  melting  at  65°-66°,  is  obtained.  A  di- 
iodide,  prepared  by  Frankforter  and  Poppe,72  is  very  unstable,  entirely 
losing  its  iodine  merely  on  standing  or  by  distilling  a  few  times. 

Anhydrous  oxalic  acid  gives  a  relatively  small  yield  of  bornyl 
esters,  dipentene  and  terpinenes  being  the  chief  products  (see  Artifi- 
cial Camphor).  Acetic  acid  at  200°  also  gives  a  certain  amount  of 
bornyl  acetate.73  The  oxalic  acid  reaction  was  the  basis  of  the  first 
industrial  process  for  the  manufacture  of  artificial  camphor. 

When  pinene  is  treated  with  HC1  in  the  presence  of  moisture,  or 
at  too  high  temperatures,  oily  mixtures  are  obtained,  the  chief  product 
being  dipentene  dihydrochloride.  Under  the  best  conditions  the  yield 
of  crystalline  bornyl  chloride  does  not  exceed  75  to  78  per  cent  of 
the  theory.  The  liquid,  oily  chloride  mixture  contains  bornyl  chloride 
in  solution,  also  dipentene  dihydrochloride  and  lesser  amounts  of  other 
substances.  Barbier  and  Grignard74  have  investigated  these  hydro- 
chloride  oils,  converting  these  hydrochloride  oils  into  the  magnesium 
compounds  and  treating  the  latter  with  oxygen  and  also  with  carbon 
dioxide.  In  addition  to  bornyl  chloride,  they  found  indications  of  the 
presence  of  fenchyl  chloride.  Aschan75  has  carefully  investigated 
these  oily  hydrochlorides,  having  at  his  disposal  comparatively  large 
quantities  of  material  made  incidental  to  the  manufacture  of  artificial 
camphor.  By  the  action  of  alkali  on  the  chlorides  he  obtained  a  com- 
plex mixture  of  hydrocarbons  and  showed  that  the  low-boiling  fraction 
contained  (1)  d.Z.bornylene  (which  yields  d.Z.camphoric  acid  on  oxida- 
tion), (2)  a  bicyclic  hydrocarbon  boiling  at  144°-145°  which  he  called 
a-pinolene,  and  (3),  a  tricyclic  hydrocarbon,  boiling-point  143°,  which 
was  quite  stable  to  permanganate  and  which  he  named  fi-pinolene  or 
tricyclene.  This  hydrocarbon,  which  has  been  obtained  as  one  of  the 
products  of  the  decomposition  of  fenchyl  chloride  by  Aschan 76  and  by 
Sandelin,77  is  probably  identical  with  the  cyclofenchene  of  Quist.78 

*J.  Am.  Chem.  Soc.  28,  1461   (1906). 
'Austerweil,  Compt.  rend.  11,8,  1197   (1909). 
*Bull.  soc.  chim.   (4)   7,  342   (1916). 
5  Ber.  1,0,  2750    (1907)  ;  Ann.  337,  27    (1912). 
•  Ann.  S87,  27    (1912). 
T  Ann.  396,  297   (1913). 
™Ann.  i*7,  278   (1918). 


440       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


By  decomposing  fenchyl  alcohol  by  heating  with  potassium  acid  sul- 
fate,  Quist  obtained  two  hydrocarbons,  one  being  the  low-boiling 
"cyclofenchene"  or  (3-pinolene.  Fenchyl  alcohol  cannot  decompose  to 
water  and  an  unsaturated  hydrocarbon,  forming  a  double  bond  with  an 
adjacent  carbon  atom,  as  will  be  evident  from  its  constitution.  Other 
hydrocarbons  may  be  formed  from  (3-pinolene  by  rearrangement.  Quist 
confirms  Aschan  as  to  its  stability  to  permanganate  but  discovered 
that  the  three-carbon  ring  is  evidently  broken  by  the  addition  of 
bromine,  forming  a  well  crystalline  dibromide  of  unknown  constitu- 
tion. The  chemistry  of  the  fenchenes  (q.v.)  into  which  these  deriva- 
tives of  pinene  lead,  is  still  in  a  very  unsettled  condition.  As  regards 
their  formation  from  a-pinene  Aschan  recalls  that  when  hydrogen 
chloride  reacts  with  tetramethyl  ethylene,  a  rearrangement  occurs. 


CH 


\ 


CH3 


HC1       CH 


—  C 


CHC1.CH3 


which  is  analogous  to  the  addition  of  HC1  to  pinene,  and  if  we  recall 

CH3 

that  the  CH2  and  >C<  groups  in  the  four-carbon  ring  are 

CH8 

equivalent  as  regards  their  spatial  relations  to  the  rest  of  the  mole- 
cule, we  may  write  the  rearrangement  of  the  initial  hydrochloride  as 
follows, 


H,C 


bornyl 
chloride 


H,C 


H2C 


BICYCLIC  NON-BENZENOW  HYDROCARBONS 
CH3  CH3 


H2C 


H9C 


CH, 


CH 


441 


H 


C< 


Cl 


CH, 


C< 


CH3 

chloride  of  fenchyl  alcohol 


According  to  Aschan  and  Quist  the  formation  of  p-pinolene  (cyclo- 
fenchene),  from  fenchyl  alcohol  or  fenchyl  chloride  is  to  be  expressed 
as  follows, 


fenchyl  alcohol 


Isopinene  is  the  name  given  by  Aschan  7g  to  a  hydrocarbon,  boiling- 


point  154.5°-155.5°,  d        0.8658,  n 


1.47025,  obtained  by  reacting 


upon  p-pinolene  with  hydrogen  chloride  and  then  decomposing  the 
hydrochloride  with  aniline.  Aschan  identified  os-apocamphoric  acid 
among  the  oxidation  products  of  iso-pinene.  Aschan  reasons  that 
isopinene,  barring  rearrangements,  can  have  only  structure  I  or  II 


T»  Chem.  Zentr.  1909  (2),  26. 


442      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


H9C 


H 


C  =  CH9     H9C 


H 
-C- 


_C  —  CH, 


H2C 


CH3  — C  — CHS 
CH CH? 


CH  —  C  —  CH 


H,C 


in 

•  v^Xl- 


Wallach  considers  that  d.Z.fenchene  has  the  constitution  represented 
by  I,  and  also  II  best  accounts  for  the  formation  of  apocamphoric 
acid. 

H                                                       H 
H2C C C  — CH3    H2C C CO-CH3 


CH,  —  C  —  CH. 


— C 

H 

isopinene 


H 
-C 


CH3  —  C  —  CH3 

C 

H 

fenchenonic  acid 

— CCLH 


ccga 


H9C 


CH3  — C  — CH, 

C 

H 

apocamphoric  acid 


C(XH 


The  formation  of  isopinene  by  the  rupture  of  the  three-carbon  ring 
in  p-pinolene  and  the  subsequent  removal  of  HC1  may  be  understood 
by  the  following  reactions, 


CH, 


)    CH, 


CHS 


H 


H 

fi-pinolene 
B.-P.  142°-144° 


•a>H 


©CH2 


H 

fi-pinolene 

hydrochloride 

M.-P.  26° 


— a— 
CHpC-CH, 


XH, 


@- 


•<DH, 


B1CYCL1C  NON-BENZEN01D  HYDROCARBONS 


443 


H, 


H 


CH/-C-CH, 


'% 


H 


"i  H 

isopinene 

Tricyclen:  When  camphene  is  treated  with  nitrous  acid,  cam- 
phenylnitrite,  C10H15N02,  is  formed80  and  when  this  derivative  is 
treated  with  concentrated  sulfuric  acid,  with  good  cooling  an  excellent 
yield  of  tricyclenic  acid  is  obtained.81  Its  constitution  has  been  shown 
by  Komppa  82  to  be  as  shown  below.  Attempts  to  oxidize  tricyclenic 
acid  or  the  hydrocarbon  tricyclene  by  permanganate  to  a  cyclopro- 
panetricarboxylic  acid,  as  Buchner  and  Weigard  have  done  in  the  case 
of  the  condensation  product  of  bornylene  (q.v.)  and  diazoacetic  ester, 
was  without  definite  result83  but  the  three-carbon  ring  in  co-amino- 
tricyclene  is  split  by  concentrated  hydrochloric  acid  to  form  cam- 
phenilane  aldehyde  and  ammonium  chloride.  The  ester  of  tricyclenic 
acid  can  be  reduced  by  the  method  of  Bouveault  and  Blanc  to  "tri- 
cyclol" and  the  latter  can  be  oxidized  by  chromic  acid  in  acetic  acid 
solution,  without  breaking  the  three-carbon  ring,  to  the  corresponding 
aldehyde.  This  aldehyde  is  readily  converted  by  the  hydrazine 
method  of  Kishner 84  and  Wolff 85  to  tricyclene,  the  yield  being  prac- 
tically quantitative.86 


CHZOH 


:HO 


GHjC-CH, 


H      H 


—c — 

r*     H    "i 

tricyclenic  acid 


CH;C-« 


H       H 


H 
^tricyclal 


^L 

CH;< 

\ 

H           H 

/ 

^ 

:-cH3 

CH3-( 

f 

•-CH, 

k 

H,        H, 

C 
H 
tricyclol 

H 

tricyclene 

Pure  tricyclene  (Lipp)  boils  at  151.6°-152°  and  melts  at  64°-65°.87 
Tricyclene  is  unchanged  by  boiling  (in  benzene)   with  zinc  chloride 

80  Jagelkische,  Ber.  32,  1501   (1902). 

"Bredt  &  May,  Chem.  Ztg.  1909,  1265. 

82  Ber.  kl,  2747   (1908)  ;  44,  1536  (1911). 

"Komppa,  loc.  cit.  Lipp,  Ber.  53.  771   (1920). 

"Chem.  Zentr.  1911   (2)    363,  1925. 

"Ann.  394,  86   (1912). 

*»Lipp,  Ber.  53,  772  (1920)  ;  tricyclol  melts  at  111°-112°  and  tricyclal  melts  at 
85°-90°  (semicarbazone  219°-220°). 

8TMoycho  &  Zienkowski,  Ann.  340,  24  (1905),  give  M.-P.  67.5°-68°,  B.-P.  152°-152.8°. 
Eijkman  (Chem.  Zentr.  1907  [2],  1210),  gives  M.-P.  66.5°,  B.-P.  152.5°.  Roth  &  Ostling 
(Ber.  46,  312  [1913]),  gives  M.-P.  62.5°-63°,  B.-P.  152°. 


444       CHEMISTRY  OF  THE  NON-BENZEN01D  HYDROCARBONS 

but  is  converted  to  camphene  by  heating  to  160°  with  sodium  bisul- 
fate. 

Tricyclene  is  also  formed  by  the  action  of  mercuric  oxide  on 
camphor  hydrazone  (v.  camphene). 

When  tricyclene  reacts  with  chloroacetic  acid,  an  ester  of  cam- 
phene hydrate  is  first  formed.88  This  and  other  evidence  indicates 
that  the  three-carbon  ring  is  easiest  broken  between  carbon  atoms  1 
and  2  or  1  and  6.  Thus  tricyclene  yields  isocamphane 89  when  hydro- 
genated  over  catalytic  nickel  at  180°,  but  when  passed  over  nickel 
at  180°  without  adding  hydrogen,  tricyclene  is  isomerized  to  cam- 
phene. Bromine  yields  a  liquid  dibromide  of  unknown  constitution. 
Hydrogen  chloride  passed  into  a  cold  ethereal  solution  of  tricyclene 
forms  a  well  crystalline  hydrochloride  melting  at  125°-127°  and 
camphene  yields  the  same  hydrochloride  under  the  same  conditions. 
Meerwein  regards  this  chloride  as  the  true  camphene  hydrochloride 
corresponding  to  Aschan's  camphene  hydrate.  This  hydrochloride 
decomposes  on  standing  at  room  temperature,  recalling  the  similar 
behavior  of  chlorinated  gasoline  and  kerosene  hydrocarbons  (of  un- 
known constitution).  Free  hydrogen  chloride,  particularly  in  alcohol 
solution,  accelerates  the  change  of  this  chloride  to  isobornyl  chloride, 
melting-point  158°. 

Beta-pinene  is  a  constituent  of  commercial  American  and  French 
turpentine  and,  according  to  Vavon,90  American  turpentine  contains 
about  27  per  cent  of  this  terpene.  Baeyer  and  Villiger  discovered 
the  sparingly  soluble  nopinic  acid  by  the  oxidation  of  turpentine  by 
cold,  alkaline  permanganate  solution.  Further  oxidation  of  nopinic 
acid  by  heating  with  lead  peroxide  (in  water)  yields  nopinone.91  This 
ketone  is  converted  to  4-isopropylcyclohexenone  by  heating  with 
dilute  acids.  The  constitutions  of  nopinone  and  nopinic  acid  have 
been  shown  to  be  those  suggested  by  Baeyer.  The  oxidation  of 
(3-pinene  by  the  customary  reactions  proceeds  normally.  The  yields 
of  the  various  oxidation  products  are  small  but  nopinic  acid  can  be 
isolated  without  great  difficulty.  Small  proportions  of  (3-pinene  can 
thus  be  detected  with  certainty. 

88  Meerwein,  Ber.  53,  1820  (1920). 
"Lipp,  Ann.  382,  265    (1911). 
90Compt.  rend.  Ufl,  997   (1909). 

91  Ber.  29,  25,  1923  (1896).  The  oxime  of  nopinone  is  an  oil,  but  tke  semicar- 
bazone  melts  at  188.5° ;  nitric  acid  oxidizes  nopinone  to  homoterpenylic  acid. 


BIG YC LIC  NON-BENZENOID  HYDROCARBONS 


445 


fi-pinene 


fi-pineneglycol 
M.-P.  75°-77° 


nopinic  acid 
M.-P.  126° 


nopinone 


By  the  use  of  Reformatsky's  reaction,  condensation  with  bromo- 
acetic  ester  by  zinc,  Wallach  made  the  nopinol  acetic  acid  which 
decomposes  with  loss  of  water  and  C02  in  two  ways  according  to  the 
conditions  employed.  By  heating  with  acetic  anhydride  p-pinene 
and  an  acid  melting  at  85°-86°  is  obtained.  Wallach92  represents 
the  synthesis  of  P-pinene  as  follows, 

o 

'  -OH 


nopinone 


nopinolacetic 
add 


ft-pinene 


Reduction  of  nopinone  gives  the  corresponding  alcohol,  nopinol,  in 
two  modifications,  a  crystal  form  melting  at  102°  and  a  liquid  form. 
By  the  Grignard  reaction  methylnopinol  (pinene  hydrate),  crystals 
melting  at  58°-59°,  and  ethylnopinol,  melting-point  43°-45°,  have 
been  prepared.  Methylnopinol  is  readily  changed  by  five  per  cent 
sulfuric  acid  to  a-terpineol,  but  nopinol  is  stable  to  dilute  acid,  illus- 
trating again  the  influence  of  changes  in  other  parts  of  the  molecule 
upon  the  stability  of  the  four-carbon  ring  in  the  pinenes.  Hydration 
also  gives  cis-terpin  hydrate,  melting  at  117°.  Heating  nopinone 
with  dilute  sulfuric  acid  gives  4-isopropyl-A2-cyclohexenone.93 

Hydrogenation  of  p-pinene  gives  pinane  identical  with  that  derived 
by  the  hydrogenation  of  a-pinene.94     p-pinene  does  not  form  a  nitro- 

"Ann.  363,  9    (1908)  ;  368,  7    (1909)  ;  356,  231    (1907).     Nopinone  melts  at  about 
0°,  boils  at  209° ;  nopinol  acetic  acid  melts  at  85°-86°. 
83  Rimini,  Ga-zz.  chim.  Ital,  tf   (2),  119   (1916). 
"Vavon,  Compt.  rend.  150,  1127   (1910). 


446      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

sochloride,  but  nitrous  acid  yields  a  nitroso-p-pinene  discovered  by 
Pesci  and  Bettelli 95  and  which  Wallach  showed  was  characteristic 
for  p-pinene.  When  turpentine  is  hydrated  by  dissolving  in  acetic 
acid  and  acetic  anhydride  and  adding  a  little  50  per  cent  aqueous 
benzene-sulfonic  acid,  the  p-pinene  reacts  first,  which  behavior  may 
be  utilized  in  purifying  a-pinene  from  p-pinene.96 

Fairly  pure  p-pinene  can  be  obtained  by  fractional  distillation  of 
the  terpenes  in  hyssop  oil,  taking  advantage  of  the  fact  that  p-pinene 
boils  approximately  10°  higher  than  ordinary  pinene;  P-pinene  from 

20° 
this  source  showed,  boiling-point  164°-166°  d^  0.8650,  n  — 1.47548. 

Wallach's  synthetic  p-pinene  showed  boiling-point   163°-164°   d^ 

22° 
0.8675,  [a]D  —25°  5',  n  —  1.4749. 


The  Fenchenes. 

Three  hydrocarbons,  known  as  a,  p  and  y-fenchenes,  are  derived 
from  the  ketone  fenchone  or  fenchyl  alcohol.  The  fenchenes  have 
not  been  positively  identified  in  any  natural  product  and  their  struc- 
ture has  been  arrived  at  by  reference  to  the  parent  substances  and, 
more  recently,  by  methods  of  synthesis.  Like  the  chemistry  of  cam- 
phene  and  bornylene,  the  chemistry  of  the  fenchenes  has  only  recently 
been  made  clear,  although  the  nature  of  the  puzzling  rearrangements 
shown  to  occur  in  this  series,  are  far  from  being  understood.  The 
current  literature  contains  a  great  deal  of  work  on  these  derivatives 
but  the  constitutions  of  the  principal  members  of  the  group  appear 
to  be  definitely  determined. 

Fenchone:  This  ketone  closely  resembles  camphor  in  its  chemical 
behavior  but  is  more  resistant  to  oxidizing  agents.  It  can  accord- 
ingly be  purified  from  other  substances  by  oxidizing  the  impurities 
with  concentrated  nitric  acid  or  by  permanganate  and  can  also  be 
prepared  readily  by  oxidizing  the  corresponding  alcohol,  fenchyl 
alcohol,  which  occurs  in  old  root  wood  of  the  yellow  pine,  Pinus 
palustris,  and  is  therefore  a  constituent  of  wood  turpentine  distilled 
from  old  stump  wood.  d-Fenchone  occurs  in  fennel  oils  and  Lien- 

"Oazz.  chim.  Ital.  16,  337  (1886)  ;  Wallach,  Ann.  Stf,  246   (1906). 
"Barbier  &  Grlgnard,  Bull.  soc.  chim.  (4)  3,  139  (1908)  ;  5,  512,  519  (1909). 


BICYCLIC  NON-BENZENOID  HYDROCARBONS  447 

chone  in  thuja  oils.97  Fenchone  does  not  form  a  hydroxymethylene 
derivative,  indicating  the  absence  of  a  — CH2  —  CO —  group.  By 
converting  fenchyl  alcohol  to  the  chloride  and  decomposing  the 
fenchyl  chloride  by  heating  with  aniline,  "fenchene"  was  produced. 
By  oxidizing  this  unsaturated  hydrocarbon  by  permanganate  oxy- 
fenchenic  acid  is  formed  which  may  be  further  oxidized  to  fencho- 
camphorone. As  a  result  of  a  detailed  study  of  these  products  and 
the  known  properties  of  fenchone  Wallach  98  proposed  the  constitutions 
shown  below  for  these  substances,  the  correctness  of  which  was  soon 
proven  by  their  oxidation  to  apocamphoric  acid.99 

H 
H_C C 


CHo  —  C  —  CH 


.  i- 

H9C 


C02H. 

H 

Hp                   r< 

P 

OH 

CH3  —  C  —  CH, 

i 

H2( 

i 

CH, 

H 

H 

oxyfenchenic  acid  fenchocamphorone 


H,C  -  C  -  C0H 


C0H 


apocamphoric  acid 

Wallach  ?s  constitution  for  fenchocamphorone  is  also  confirmed  by  its 
synthesis  in  a  very  direct  manner,  by  decomposing  the  lead  salt  of 
homoapocamphoric  acid  by  heating,100 
H9C  -  CH  -  C02H  H2C  -  CH  -  CO 

II  II 

I  CH3-C-CH3  -  >  CH3-C-CH3 

H2C  -  CH  -  CH2  —  C02H  H2C  --  CH 


I*7  Fenchone  melts  at  5°  to  6°.     The  physical  properties  of  a  specimen  regenerated 
from  the  semicarbazone  [Wallach,  Ann.  562,  195   (1908)]  were  as  follows,  boiling-point 

I  192°-193°,  d18o  0.948,   [a]D+  62.76°    (higher  in  alcohol  solution)    n^-1.46355.     Fen- 

chone does  not  form  a  phenylhydrazone  but  readily  gives  an  oxime,  d.  and  I.  melting  at 
164°-165°,  inactive  form  melting  at  158°-160°  [Wallach,  Ann.  272,  104  (1893)].  The 
semicarbazone  forms  very  slowly  ;  Wallach  recommends  allowing  an  alcoholic  solution 
of  the  ketone,  semicarbazid  hydrochloride  and  sodium  acetate  to  stand  for  two  weeks 
[Ann.  353}  211  (1907)].  The  semicarbazone  crystallizes  from  dilute  alcohol  in  long 
prisms  melting  at  182°-183°. 

88  Ann.   SOO,  320. 

"Ann.  315,  293   (1901). 

1(WKomppa,  Ber.  kk>  395  (1911).  The  racemic  semicarbazone  of  fenchocamphorone 
f  melts  at  220°. 


448      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

By  reacting  upon  a-fenchocamphorone  with  methyl  magnesium 
iodide  Komppa  and  Roschier101  have  synthesized-a- fenchene.  The 
tertiary  alcohol  formed  by  this  reaction  is  decomposed  by  distilling  at 
ordinary  atmospheric  pressure  to  give  the  hydrocarbon. 

OH 
CH, CH C  =  0  CH2 CH 


JH2 

CH2 CH C  — CH3  CH2 CH C  =  CH2 

CH3-C-CH3     [  or 

!H- 


>^ 

A, 


The  physical  properties  and  chemical  behavior  of  the  synthetic 
a-fenchene 102  are  practically  identical  with  Aschan's  isopinene  (q.v.), 
but  Wallach  considers  that  a-fenchene  contains  the  >C  =  CH2  group, 
on  account  of  its  formation  together  with  p-pinene  when  nopinolacetic 
acid  is  dehydrated.103 

In  a  similar  manner  Komppa  and  Roschier  have  treated  d.Z.p-fen- 
chocamphorone  with  magnesium-methyl  iodide,  thus  forming  methyl- 
p-fenchocamphorol.104  When  this  alcohol  is  heated  with  potassium 
acid  sulfate  a  mixture  of  two  unsaturated  hydrocarbons  is  obtained, 
consisting  mainly  of  d.Lp-fenchene  and  an  endocyclic  hydrocarbon 
y-fenchene.  The  (3  hydrocarbon  yields  d.l.  hydroxy-p-fenchenic  acid 
melting  at  124°-125°  on  oxidizing  with  permanganate,  and  on  further 
oxidation  by  the  lead  peroxide  and  sulfuric  acid  method  d.Z.p-fencho- 
camphorone  is  obtained.  The  latter  ketone  by  further  oxidation 
yields  apofenchocamphoric  acid.  A  fourth  fenchene,  termed  isoallo- 
fenchene  by  Semmler,  and  isofenchylene  by  Quist,  is  called  5  or  iso- 
fenchene  by  Komppa.  The  p-fenchene  of  Komppa  is  Wallach's 
D,  d.  or  L.  I.  fenchene,  or  Semmler's  isofenchene. 

101 J.  Chem.  Soc.  in  (1),  466   (1917). 

102  The   synthetic  hydrocarbon   of   Komppa    boils  at   154°-156°,   has   a   density    ^ 

20° 
0.8660   and    refractive   index    ^-    1.47045.     The    hydrochloride,    melting-point    35°-37° 

is  identical  with  that  made  from  isopinene.  Ozone  gives  racemic  fenchocamphorone 
and  r  a-fenchenylanic  acid,  melting-point  105°. 

1<aAnn.  363,  3    (1908). 

™Chem.  Ate.  13,  2864  (1919).  Fenchocamphorol  melts  at  66*-67°  and  boils  at 
77°  (9mm.)  ;  y-fenchene  boils  at  146°-148°,  d^£  0.8539. 


CH3 
CH3 


>C 


BICYCLIC  NON-BENZENOID  HYDROCARBONS 

H  CH3  H 

— — C 


449 


CH 


H,C 


CH2 

— C 

H  OH. 

methyl-p-fenchocamphorol 


CH3 
CH3 


H 
-C 


CH 


CH3 


H 

y-fenchene 


—  CH3 


Fenchone  itself  has  been  synthesized  by  Ruzicka 105  in  the  manner 
indicated  by  the  following  reactions. 

(1)  Levulinic  ester  and  ethyl  bromoacetate  are  condensed  by 
means  of  zinc  and  the  resulting  lactonic  ester  is  converted  into  the 
I  nitrile  by  treating  with  potassium  cyanide, 


H9C  — CO  — CH, 


CH. 

H2C  —  C  —  CHXXXR 


HC  —  C0CH 


BrCH2.C02R 


\ 


OH 


>H,C—  C02C2H5 


CH3  CH3  CH3 

|H2C  —  C  —  CH2C02R         H2C  —  C  —  CN         H2C  —  C  —  C02H. 


\ 
( 

—  CO 


0 


C, 


C, 


H,C02R  -»      1       CH2-C02H. 
H2C  —  C02R  H2C  —  C02H . 


(2)  The  above  tricarboxylic  acid  is  condensed  to  a  cyclopen- 
jtanone  derivative  by  means  of  sodium  in  benzene,  and  the  ester  of  the 
suiting  product  is  condensed  with  bromoacetic  ester. 


Ber.  50,  1362  (1917), 


450      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 
CH3 

__i_C02R 

4-Br.CH2C02R 


Hc 


HC  —  C  = 


H2C  —  C  —  C02R 

I     AH, 

H2C  —  C  —  CH2C02R 
OH 


(3)  The  above  hydroxy  acid  is  converted  to  the  unsaturated  acid 
and  the  latter  reduced  to  the  saturated  acid.    , 


CH3 
H2C  — C  — C02R 

CH2 
H2C  —  C  =  CH.C02R 


CH3 

H2C  — C C02R 

CIL 


H. 


-As 


•CHoCOoR 


(4)  On  heating  the  lead  salt  of  the  above  acid  methylnorcamphor 
is  formed  which  on  methylating  by  Haller's  method,  using  sodium 
amide  and  methyl  iodide,  fenchone  and  fenchosantenone  are  formed. 


CH, 


H,C  —  C 


C02H 


CH2 


H. 


CH  — CH2  — C02H 


CHS 
H2C  — C CO 

I     AH 

CH2      , 

H2C  — CH  — CH2 

methylnorcamphor 


H9C 


H. 


CH3 
Aro 

CH3 

HP        p           r 

CH          1 

P        I 
.     rn        rn     nn 

->     |       {H,      ; 

prn        CH        r 

fenchosantenone 


fenchone 


CH3 
CH, 


The  above  structure  of  fenchone  explains  the  formation  of  fencholic 
acid  from  fenchone  by  heating  with  caustic  potash.106 

"•Wallach,  Ann.  369,  71  (1909). 


BICYCLIC  NON-BENZENOID  HYDROCARBONS 
CH3  CH3 

H2C-  -C-      -CO  H2C C CO,H. 

CH2          |  by  KOH          [  C 

_iH_i<CH3 
CH3 


451 


H 


H 


CH, 

CH CH< 

CH3 


fencholic  acid 


By  the  action  of  sodium  or  potassium  acid  sulfates  on  fenchyl 
alcohol  at  170°-180°,  in  a  current  of  carbon  dioxide,  a  fenchene  is 
obtained  boiling  at  151°-153°,  D  0.8660.  On  oxidation  it  yields 
hydroxyfenchenic  acid  melting  at  138°-139°.107 

Fenchyl  chloride,  like  the  higher  alkyl  halides  in  general,  reacts 
very  slowly  with  magnesium  in  ether.  After  one  week  and  treating 
with  carbon  dioxide  the  reaction  mixture  gives  chiefly  hydrofenchene 
carboxylic  acid  and  hydrodifenchene.108 


—  C02H 


CH3 

CH            r           r 

k    | 

CH2  C  C< 

CH3 

X* 
S* 

H 

CH3 

hydrodifenchene 

H  CH3 

hydrofenchenecarboxylic  acid 

M.-P.  45°^6° 
(racemic  acid  M.-P.  52°-53°) 


By  the  action  of  ozone  on  a-fenchene  Komppa  and  Hintikka  109 
obtained  fenchocamphorone,  which  behavior  is  also  readily  explained 
by  Wallach's  formula  for  this  hydrocarbon. 


H 


C  =  0 


107 </.  Chein.  Soc.  112,  398   (1917). 
08  Komppa  &  Hiutikka,  Ber.  46.  645   (1913). 
109  Ber.  +7,  936  (1914). 


452       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

The  saturated  hydrocarbon,  fenchane,  has  been  prepared  by  Kish- 
ner's  admirable  method.    By  heating  d.fenchone,  [a]     -f  62.8°,  with 

hydrazine  hydrate  the   d.hydrazone   is   first   formed    (melting-point 
56°-57°)   and  by  heating  the  hydrazone  with  sodium  ethylate  fen- 

20° 
chane  is  formed,110  boiling-point  149°,  d—  0.8316  and  laevorotatory 

[a]n  — 18.11°  (4  per  cent  solution  in  alcohol). 

»o  Wolff,  Ann.  S9k,  86   (1912). 


Chapter  XIII.      Bicyclic  Non-benzenoid 
Hydrocarbons. 

Camphene  and  Bornylene. 

Although  these  two  hydrocarbons  have  quite  different  structures 
they  are  considered  together  on  account  of  their  relations  with  pinene 
and  bornyl  halides,  and  with  borneol  and  camphor.  Until  recent 
years  the  existence  of  bornylene,  as  distinguished  from  camphene,  was 
not  recognized.  The  chemistry  of  these  two  hydrocarbons,  particu- 
larly that  of  camphene  and  its  oxidation  products,  is  somewhat  in- 
volved but  by  1914  the  accumulation  of  evidence  was  such  that  the 
constitution  of  these  two  hydrocarbons  could  be  considered  as  estab- 
lished beyond  any  reasonable  doubt.  Particularly  is  this  true  since 
the  synthesis  of  camphenic  acid  by  Lipp  x  and  the  investigations  of 
Haworth  and  King.2 

Camphene  and  bornylene  are  both  solid  and  crystalline  at  ordinary 
temperatures,  but  only  camphene  has  been  found  in  nature,  occurring 
in  both  d.  and  I.  forms.  Camphene  was  early  recognized  as  a  product 
of  the  decomposition  of  bornyl  chloride,  the  ^.chloride  giving  I.  cam- 
phene and  the  d.chloride  giving  d.  camphene.3 

Although  camphene  crystallizes  well  and  purification  by  recrystal- 
lization  has  been  carried  out  in  most  cases,  the  physical  properties 
reported  for  camphene  are  far  from  being  in  agreement.  The  dif- 
ferences noted  in  physical  properties  are  doubtless  due  to  the  presence 
of  bornylene  or  to  some  other  as  yet  unidentified  hydrocarbon. 

When  borneol  derivatives  are  decomposed  to  hydrocarbon  under 
milder  conditions  the  chief  product  is  bornylene,  a  hydrocarbon  first 
recognized  by  Wagner.4  Bornyl  iodide,  made  from  borneol  and  hydri- 
odic  acid  (which  is  identical  with  the  product  of  HI  and  pinene), 
gives  mainly  bornylene  on  treating  with  alcoholic  caustic  alkali. 

1Ber.  47 f  871    (1914). 
*J.  Chem.  Soc.  105,  1342   (1914). 

"Berthelot,  Ann.  10,  367    (1859);   Kachler,  Ann.  119,  96    (1879);  Tilden  &  Arm- 
strong, Ber.  12,  1753   (1879). 
*Ber.  32,  2302  (1899). 

453 


454       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


Q 


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O  o       0^        o^     o 

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s  g 


>'      o1 


000 


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ine 


s  & 

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ft 

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s   s 


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t-id  CO-^iO 


13 


BICYCLIC  NON-BENZENOID  HYDROCARBONS  455 

Also  when  borneol  xanthogenate  is  heated  it  decomposes  to  give  chiefly 
bornylene,  a  method  discovered  by  Tschugaeff.5  Henderson  and 
Caw6  showed  that  when  bornylene  is  prepared  by  Tschugaeff's 
method,  the  impurities  can  be  removed  by  oxidizing  with  hydrogen 
peroxide,  the  bornylene  so  purified  melting  at  113°,  and  boiling  at 
146°-147°  (750mm.).  Bornylene  has  recently  been  made  from  cam- 
phor by  Ruzicka  7  by  the  conversion  of  camphor  to  bornylamine  by 
heating  with  ammonium  formate  in  an  autoclave  at  60  atmospheres 
pressure;  the  resulting  amine  was  subjected  to  the  method  of  exhaus- 
tive methylation  with  methyl  iodide  (bornyltrimethylammonium 
iodide  melts  at  245°).  The  free  trimethyl  base  is  gently  decomposed 
to  give  bornylene  melting-point  111°-112°. 

Bredt  has  also  made  a  very  pure  bornylene  from  camphocarboxylic 
acid.  By  electrolytic  reduction  of  this  acid  to  the  corresponding 
hydroxy  acids  8  and  distilling  the  acetylborneolcarboxylic  acid  the 
unsaturated  acid,  bornylenecarboxylic  acid,9  is  obtained  and  on  react- 
ing upon  this  acid  with  hydrogen  bromide  a  mixture  of  a  and  (3-bro- 
mocamphanecarboxylic  acids  are  obtained.  The  p-bromo  acid  is 
decomposed  on  heating  with  aqueous  alkali  to  bornylene,  bornylene- 
carboxylic acid  and  a  lactone. 


CH.C02H  CH.C02H  C  —  CO2H. 

->  C8H14<  || 
.OH.  CH 


. 

C8H14<  |  ->  C8H14<  |  ->  C8H14<  ||  +  HBr 

C  =  0  CH. 


CH.CCXH  CBr.C02H. 

-  >  C8H14<  |  and    C8H14<  | 

CHBr        \  CH2 

fi-bromocamphene-  \ 

carboxylic  acid.  \  CH 

C8H14<||  bornylene 

CH. 

The  bornylene  thus  obtained  had  the  following  physical  properties, 
melting-point    113°,    boiling-point    146°     (740mm.),    [a]     —21.69° 

(10.4%  in  toluene),  [a]     —26.96°   (4.42f0  in  methyl  alcohol). 
Bornylene  gives  camphoric  acid  on  oxidation,  which  indicates  that 

5  Tschugaeff  &  Budrick,  Ann.  388,  280   (1912). 
a«7.  Chem.  Soc.  103,  1543   (1912). 

7  Helv.  chim.  Acta.  3,  48    (1920). 

8  Bredt,  Ann.  366,  1  (1909).     These  are  ois  and  cis-trans  isomeric  forms  of  borneol- 
carboxylic  acid,  the  cis  acid  melting  at  102°-103°  and  the  cis-trana  melting  at  171°. 

•Melting-point  112°-113°,  boiling-point  158°  at  13mm. 


456      CHEMISTRY  OF  THE  NON-BENZEN01D  HYDROCARBONS 


the  double  bond  is  in  the  position  shown,  which  structure  is  that  for 
merly  supposed  to  represent  the  constitution  of  camphene, 
CH3  CH3 

-C CH  CH2 C— 


CH 


CH, 


-C-CH, 
CH  — 


H 


CO,H. 


CH 


CH, 


-C-C 
-C 


H, 


H 


-C02H. 

camphoric  acid 


bornylene 

Camphene  forms  an  ozonide  which  on  decomposition  gives  formal- 
dehyde-camphenilone  and  dimethylnorcampholide.10  Komppa  and 
Hintikka  "  have  synthesized  the  latter  substance  and  shown  its  con-| 
stitution  to  be  as  represented  in  the  following. 

CH3  CH3 

CH2 CH C< 


CH2 

in 


CH3 


0 


camphene   (Wagner) 


and 


O'-L-  I>2 

CH2 

^^ 

o 

o       r\ 

^J-J^                     V_^J.J.      -               \^   -••—   V/ 

dimethylnorcampholide 

=  0 


camphenilone 

This  constitution  of  camphenilone  is  supported  by  the  fact  that  iti 
does  not  form  a  hydroxymethylene  compound12  and  therefore  does 
not  possess  a  CH2  group  adjacent  to  the  carbonyl  group.  Further 
evidence  of  the  structure  of  camphenilone  is  given  by  the  conversion 
of  camphenilone  by  the  action  of  sodamide,  to  the  amide  of  the  acid, 

CH3 


CH, 


CH- 
H2 


v^ 

i 


CH< 


CH, 


CH 


which  substance  has  also  been  synthesized.13 

10  Harries  &  Palmen,  Ber.  A3.  1432   (1910). 

llBer.  42,  898    (1909). 

"Moycho  &  Zienkowski,  Ann.  31,0,  54    (1905). 

"Bouveault  &  Blanc,  Compt.  rend.  Uft,  1314  (1908), 


BICYCLIC  NON-BENZENOID  HYDROCARBONS  457 

When  camphene  is  oxidized  by  alkaline  permanganate  the  chief 
product  is  camphenic  acid,  C10H1604,  an  acid  isomeric  with  camphoric 
acid.  A  great  deal  of  work  has  been  done  upon  the  structure  of  this 
acid,  based  upon  which  other  constitutions  for  camphene  have  been 
proposed.14  However  no  reasonable  doubt  should  exist  as  to  its  con- 
stitution since  its  synthesis  by  Lipp,15  in  the  following  manner:  The 
ethyl  ester  of  1 . 3-cyclopentanonecarboxylic  acid  was  condensed,  by 
Reformatsky's  reaction,  with  a-bromoisobutyric  ester  in  the  presence 
of  zinc.  By  decomposition  with  loss  of  water  an  unsaturated  acid 
was  formed,  whose  constitution  may  be  either  III  or  IV  but  on  hydro- 
genating  the  saturated  acid  1.3-carboxylcyclopentylisobutyric  acid 
was  formed,  which  proved  to  be  identical  with  dJ.cis-camphenic 
acid.16 

OH 

CH3 

CH2 CO  CH2 C C< 

I      CH3 
CH2  >  CH2     C02R.       > 

CH2 CH .  C02R  CH2 CH  —  C02R . 

I.  II. 

CH3  CH3 


—  ^  ^<^ 
1     CH3 
CH       C02R 

v^n 

•  I 

-     \u  — 
CH2 

^<^ 
1     CH 
C02R 

ATI       rjo  T> 

L 

UUg— 

is 

C02R 

III.   * 

IV. 

CH3 

CH 

CH 

-c< 

1 

CH2 

1     CH3 
C02H 

r,TT 

A* 

ro  TT 

camphenic  acid 

When  camphenic  acid  is  distilled  it  loses  C02  to  form  a  ketonic 
acid,  camphenonic  acid,  whose  constitution  may  be  inferred  from  the 
structure  of  camphenic  acid.  The  d.  and  L  forms  of  camphenonic 

JJCf.  review  by  Haworth  &  King,  J.  Chem.  Soc.  101,  1975  (1912). 

18  Camphenic  acid  is  practically  insoluble  in  cold  water,  ligroin  and  carbon  bisul- 
fide, but  crystallizes  from  hot  water,  melting-point  135°-137°. 


458       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


acid  together  with  the  d.l.  acid  are  formed  from  camphenic  acid  made 
by  the  oxidation  of  strongly  d.  or  I.  camphene.17 

CH  CH 


—  v_> 

I 


CH- 
H2 


CH, 


CH 


C< 

I    CH3 

C02H         ±^ 


C(XH 


CH2 


CH 


C< 


CH3 


CH2 C C02H. 

camphenonic  acid. 


camphenic  acid 

Fusion  of  camphenonic  acid  with  caustic  alkali  or  treatment  with 
sodium  and  alcohol  regenerates  camphenic  acid. 

Wagner's  constitution  for  camphene  is  also  supported  by  the  work 
of  Buchner  and  Weigand,18  who  condensed  camphene  with  diazo- 
acetic  ester  and  oxidized  the  acid  so  obtained  to  1 . 1 . 2-cyclopropane- 
tricarboxylic  acid.  The  camphene  employed  by  Buchner  melted  at 
44°-45°  and  distilled  at  156°-157°.  Treatment  with  the  ester  at 
160°-165°  in  the  presence  of  copper  powder  gave  vigorous  evolution  of 
nitrogen  and  a  good  yield  of  the  condensation  product,  2 . 2-dimethyl- 
norcamphane-3-spirocyclopropanemethylcarboxylate.  The  relation 
of  camphene  to  the  condensation  product  and  the  oxidation  product 
are  as  follows: 


CH; 


CH, 


H 

camphene 


H 
rj 

CH3 
n      PH 

CH2 

H 

\/ 

CH.C02R 

CCLH. 


CH, 


C02H.     CH.C02H. 

The  spiro  ester  is  stable  to  permanganate  in  suspension  in  sodium 
carbonate  solution.     [Buchner  and  Weigard  also  succeeded  in  mak- 

"Aschan,  Ann.  1,10,  240   (1915). 
"Ber.  46,  759  (1913). 


BICYCLIC  NON-BENZENOID  HYDROCARBONS 


459 


ing  the  acid  chloride,  from  which  the  amide  was  prepared,  leaflets 
melting  at  124°.]  The  purified  amide  readily  yields  the  pure  acid, 
melting  at  108°.  Reduction  of  the  ester,  by  sodium  in  absolute 
alcohol,  converts  the  C02R  group  to  CH2OH  with  rupture  of  the 
cyclopropane  ring. 

Applying  the  same  method  to  bornylene  Buchner  and  Weigand19 
obtained  1 . 2 . 3-cyclopropane  tricarboxylic  acid. 


CH.C02H 


CH.CXXH. 


When  camphene  hydrochloride  is  carefully  treated  with  dilute 
alkali,  camphene  hydrate  is  formed,  which  can  be  decomposed  to 
camphene  having  the  same  rotatory  power  as  the  original  hydrocar- 
bon. The  hydrate  is  therefore  formed  without  causing  any  change 
in  the  carbon  structure  of  camphene.  Only  two  formula  for  this 
hydrate  are  possible,  one  being  a  tertiary  and  one  a  primary  alcohol, 
but  the  properties  of  camphene  hydrate  are  clearly  those  of  a  tertiary 
alcohol,  i.e., 


camphene  hydrate 

19  Ber.   46,   2108    (1913).     The   trimethyl   ester   of   1.2.3-cyclopropanetricarboxylic 
acid  melts  at  56°-57°,  which  serves  to  distinguish  it  from  its  isomers. 


460       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

A  stereoisomeric  form  of  camphene  hydrate  is  methylcamphenilol, 
obtained  by  the  action  of  magnesium-methyl  iodide  on  camphenilone. 
Both  forms  yield  camphene  on  dehydration  and  probably  bear  a 
stereochemical  relation  with  each  other  comparable  to  borneol  and 
isoborneol.20 

To  explain  the  rearrangement  which  occurs  when  isoborneol  is 
decomposed  to  form  camphene,  the  intermediate  formation  of  tri- 
cyclene  has  usually  been  assumed, 


=CH2 

/CH, 

CH3 


isoborneol 


ene 


tric^clene 

Tiffeneau21  has  proposed  the  theory  that  when  alcohols  are  decom- 
posed with  the  formation  of  a  hydrocarbon  of  a  different  carbon 
structure,  as  in  the  decomposition  of  pinacoline  alcohol  to  tetramethyl- 
ethylene,  that  the  intermediate  product  is  a  hydrocarbon  having  a 
bivalent  carbon  atom.  In  the  case  of  isoborneol  and  its  decomposi- 
tion to  camphene  this  would  be  represented  as  follows, 


"Aschan,  Ann.  W,  222    (1915). 
gen.  d.  8ci.  18,  583  (1907). 


BICYCLIC  NON-BENZEN01D  HYDROCARBONS  461 

Meerwein  22  has  tested  both  of  these  hypotheses.  Camphor  hydra- 
zone  is  decomposed  by  mercuric  oxide,  the  intermediate  compound 

CH2 
C8H14<  I 

C •  =  N.NH.HgOH  being  decomposed  with  evolution  of  nitro- 
gen, and  it  is  a  reasonable  supposition  that  the  bivalent  carbon  com- 

CH2 

C8H14<  | 

pound  C<  whose  transitory  existence  is  assumed  by  the  Tif- 

feneau  theory,  would  be  formed  and  immediately  rearrange  to  cam- 
phene,  if  this  theory  is  correct.  It  is  found,  however,  that  tricyclene 
is  formed  almost  quantitatively. 

The  properties  of  tricyclene  clearly  show  that  it  cannot  be  an  in- 
termediate product  in  the  conversion  of  isoborneol  to  camphene. 
Thus  Meerwein  shows  that  under  the  conditions  by  which  isoborneol 
is  almost  quantitatively  changed  to  camphene  (heating  with  33% 
sulfuric  acid  at  100°),  tricyclene  is  practically  unchanged.  Also,  as 
shown  by  Lipp,23  heating  tricyclene  with  fused  zinc  chloride  is  with- 
out effect  although  isoborneol  is  decomposed  to  camphene  under  these 
conditions. 

As  regards  the  opposite  reaction,  the  conversion  of  camphene  to 
isoborneol  (or  acetate) ,  Meerwein  shows  that  chloroacetic  acid  reacts 
more  rapidly  with  camphene  than  with  tricyclene,  and  consequently 
tricyclene  cannot  be  an  intermediate  product  in  the  conversion  of 
camphene  to  esters  of  isoborneol.  In  these  experiments  evidence  was 
found  that  tricyclene  first  forms  an  ester  of  camphene  hydrate.  When 
tricyclene  or  camphene  is  treated  with  hydrogen  chloride  in  cold 
ethereal  solution,  a  very  unstable  hydrochloride  is  formed  which  Meer- 
wein regards  as  the  true  chloride  of  camphene  hydrate.  It  is  so 
unstable  that  on  merely  shaking  the  chloride  with  water  at  ordinary 
temperatures,  camphene  hydrate  is  formed;  in  alcoholic  caustic  potash 
the  neutralization  of  the  alkali  takes  place  so  rapidly  that  the  per 
cent  of  the  hydrochloride  present  can  be  titrated  in  the  cold  with 
N/2  caustic  solution  during  one  half  hour.  The  most  striking  prop- 
erty of  this  hydrochloride  is  its  rearrangement  to  the  chloride  of 
isoborneol,  melting-point  158°,  which  takes  place  on  warming  with 
alcoholic  hydrochloric  acid,  which  probably  accounts  for  the  fact  that 
this  camphene  hydrochloride  was  discovered  only  very  recently.2* 

KBer.  53,  1815  (1920). 
2S  Ber.  53,  769  (1920). 
2«  Meerwein,  loc.  cit. 


462       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

Thus,  when  hydrogen  chloride  is  passed  into  a  solution  of  camphene 
in  alcohol  the  product  is  mainly  isobornyl  chloride,  but  also  contains 
more  or  less  true  camphene  hydrochloride,  thus  accounting  for  the 
various  melting-points  recorded  in  the  literature  for  camphene  hydro- 
chloride,  i.e.,  118°  to  158°.  This  chloride  melting  at  158°  is  the  iso- 
bornyl chloride,  evidence  for  which  is  its  reduction  by  sodium  and 
alcohol  to  camphane  (dihydrobornylene)  and  its  conversion  to  iso- 
bornyl acetate  by  treating  with  silver  acetate  in  glacial  acetic 
acid. 

Isobornyl  chloride  is  much  more  stable  than  camphene  hydro- 
chloride  and  is  practically  not  affected  by  alcoholic  caustic  alkali  at 
ordinary  temperatures.  Nevertheless  isobornyl  chloride  is  consider- 
ably less  stable  than  bornyl  chloride  (made  from  pinene  and  HC1) 
since  by  heating  for  one  hour  with  alcoholic  caustic  alkali  bornyl 
chloride  is  scarcely  attacked 25  but  isobornyl  chloride  is  completely 
decomposed.  In  such  a  chloride  mixture  it  is  therefore  possible  to 
estimate  fairly  accurately  the  per  cent  of  camphene  hydrochloride, 
isobornyl  and  bornyl  chlorides,  by  making  use  of  their  relative  stabil- 
ities to  caustic  alkali. 

The  facts  point  to  reversible  reactions  between  camphene  and 
esters  of  camphene  hydrate  (chloride  or  acetate),  and  between  the 
latter  and  esters  of  isoborneol. 


0/\c 


camphene 


acetate  of 
camphene  hydrate 


isobornyl  acetate 


Thus,  camphene  hydrate  can  be  prepared  from  isobornyl  chloride. 
Methyl  borneol  and  methyl  fenchyl  alcohol  also  appear  to  be  in 
equilibrium  in  the  presence  of  acids  since  Ruzicka  26  finds  that  by 
the  action  of  sodium  acid  sulfate  on  either  of  these  alcohols,  the  same 
mixture  of  methylcamphene  and  methyl-a-fenchene  is  obtained. 

"Hesse,  Ber.  39,  1127   (1906). 
**Helv.  chim.  Acta.  1,  110   (1918). 


BICYCL1C  NON-BENZENOW  HYDROCARBONS 
CH3  CM, 


463 


CH;C-CH, 


or 


methylborneol  methylfenchyl  alcohol 

Although  Meerwein  has  produced  good  evidence  to  show  that  in 
the  isoborneol  ±5  camphene  rearrangement  the  intermediate  formation 
of  tricyclene  or  a  hydrocarbon  containing  bivalent  carbon  is  extremely 
improbable,  the  mechanism  of  the  rearrangement  is  as  obscure  as 
ever.  This  rearrangement  is  to  be  classed  with  others  such  as  that 
discovered  by  Kishner.27 

OH 
CH,  / 


CH2  — CH  —  C< 


CH, 


CH, 


CH  CH3 

\   / 
C 

CH2          CH3 


and  the  well-known  retropinacoline  rearrangements;  for  example,  the 
chloride 

CH3 

\  CH3 


CH3 
CH, 


C.CH2C1 


>C  — CH2CH3 

CH- A, 


and  the  like. 

By  the  hydrogenation  of  camphene  and  bornylene  the  correspond- 
ing saturated  hydrocarbons  are  obtained,  the  nomenclature  of  which 
is  unfortunate.  By  reducing  bornylene  by  the  method  of  Sabatier 
and  Senderens  a  "camphane"  melting  at  150°  and  boiling  at  161°-162° 
was  obtained  by  Henderson  and  Pollock  28  and  the  same  hydrocarbon 
in  a  somewhat  purer  form  was  obtained  from  camphor  by  the  decom- 
position of  the  hydrazone,29  according  to  the  method  of  Kishner,  the 
hydrocarbon  made  in  this  way  having  a  melting-point  of  156°-157° 
and  boiling  at  161°  (757  mm.).  From  its  relation  to  camphor  it  is 

27  Chem.  Zentr.  1908  (2),  1342;  1911  (1),  543. 

28  J.  Chem.  Soc.  97,  1620   (1910). 
"Wolff,  Ann.  394,  86   (1912). 


464       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


perhaps  proper  to  call  it  camphane,  which  however  confuses  it  with 
the  isomeric  hydrocarbon  derived  from  camphene.  The  terms  dihy- 
drocamphene  and  dihydrobornylene  are  much  to  be  preferred. 

By  heating  isoborneol  with  zinc  dust  at  220°  Semmler30  obtained 
a  hydrocarbon,  C10H18,  boiling  at  162°  and  melting  at  85°,  and 
Vavon31  reduced  camphene  in  ether  solution  by  platinum  black  and 
hydrogen  and  obtained  a  hydrocarbon  probably  identical  with  Semm- 
ler 's  melting  at  87°.  Sabatier  and  Senderens  obtained  a  liquid  mix- 
ture from  camphene  which  Henderson  and  Pollock32  showed  was  a 
mixture  of  the  camphane  of  Vavon  and  unsaturated  hydrocarbons. 
The  crude  product  obtained  by  Henderson  and  Pollock  melted  at  64° 
and  the  product  obtained  by  Ipatiev,33  "isocamphane,"  obtained  by 
passing  isoborneol  over  a  mixture  of  nickel  oxide  and  alumina  at 
215°-220°  with  hydrogen  at  110  atmospheres,  and  described  as  melt- 
ing at  63°-64.5°,  is  probably  the  crude  camphane. 

A  product  called  cy do camphane  has  been  made  from  cyclocam- 
phanone  by  Kishner's  hydrazine  method.  Cyclocamphane  melts  at 
117°-118°.34  Angeli,35  who  first  prepared  the  ketone  by  the  action  of 
nitrous  acid  on  aminocamphor,  regarded  it  as  an  unsaturated  ketone 
and  accordingly  called  it  "camphenone."  The  presence  of  the  three- 
carbon  ring  in  camphanone  was  shown  by  converting  it  (through  the 
oxime  and  nitrile  and  oxidation)  to  cyclocampholenic  acid  and  by 
further  oxidation  to  cycloisocamphoronic  acid. 


CO 


CH3CCH3 


CQH 
CQH    CQH  I       CO,H 


cyclocamphane  cyclocamphanone  cyclocampholenic  cycloisocamphoronic 

acid  acid,  M.-P.  228° 

Reduction  of  the  ketone  yields  a  new  borneol,  cyclocamphanol,  melt- 
ing-point 174°-176°. 

Camphene,  like  |3-pinene,  does  not  form  a  nitrosite  but  the  nitrosite 

"Ber.  S3,  77 Q   (1900). 

"Compt.  rend.  149,  997  (1909). 

*2  J.  Ohem.  Soc.  107,  1620   (1910). 

MBer.  ft,  3205    (1912). 

"Holz,  Z.  cmgew,  Chem.  27   (1),  347   (1914). 

**6azz.  chim.  Ital.  24   (2),  44,  317   (1894). 


BICYCLIC  NON-BENZEN01D  HYDROCARBONS 


465 


conceivably  formed  as  a  labil  intermediate  product,  decomposes  to 
give  nitrocamphene 36  (melting-point  of  d  and  I  forms  84°-85°,  d.l.- 
nitrocamphene  melting  at  64°-66°).  Bromine  also  shows  a  similar 
behavior,  the  group  >C  =  CH2  adding  Br2  to  form  the  labil 
>CBr  —  CH2Br  which  immediately  decomposes  to  give  the  mono- 
bromo  derivative  >C  =  CHBr,  camphenylidene-6-bromomethane.37 
This  bromide  is  capable  of  combining  with  hydrogen  bromide  (prob- 
ably reversible)  to  form  2-bromo-Q-bromo-camphene,  melting  at 
90°-91°.  The  corresponding  camphenylidene  chloride  is  inert  to 
hydrogen  chloride. 

Camphene  condenses  with  formaldehyde  (trioxymethylene)  in 
acetic  acid,  to  form  a  primary  alcohol,  from  which  a  large  number  of 
derivatives  have  been  prepared.  Thus,  oxidation  of  the  new  alcohol 
yields  the  corresponding  aldehyde,  which  can  then  react  with  mag- 
nesium alkyl  halides  to  give  a  series  of  diethylenic  hydrocarbons  of 
the  camphenic  type. 

Camphene  combines  with  hypochlorous  acid  in  cold  dilute  solu- 
tions to  give  a  nearly  quantitative  yield  of  camphenechlorohydrin, 
melting  at  93°.  Reduction  of  this  chlorohydrin  with  zinc  and  alcohol 
gives  isoborneol;  camphenechlorohydrin  is  therefore  probably  a-chlo- 
roisoborneol.38  Camphenechlorohydrin  reacts  with  caustic  alkalies  or 
moist  silver  oxide  to  form  camphenilane  aldehyde,  which  is  also 
obtained  by  treating  campheneglycol  (obtainable  by  permanganate 
oxidation  of  camphene)  with  dilute  acids.  The  conversion  of  1.2- 
glycols  to  aldehydes  or  ketones  by  dilute  acids  is  quite  a  general 
reaction.  The  principal  oxidation  products  of  camphene  are  shown 
in  the  following  diagram, 


OH 
-C-CO.H 


CH, 


camphene 


H, 


CMJ 


camphene  glycol 
M.-P.  200° 


CH, 


a-oxycamphenilanic 
acid,  M.-P.  171° 


*«Lipp,  Ann.  S99,   241   (1913). 

•'Langlois,  Ann.  chim.  12,  265   (1920). 

"  Henderson,  Heilbron  &  Howie,  J.  Ctem.  Soo.  105,  1367  (1914). 


466       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

n C-CHO 


H 

CH        \^ 

r    l^ 

CH,       | 

camphenilane  aldehyde  camphenilanic  acid  camphenilone 

M.-P.  70°  M.-P.  65°  M.-P.  43° 

Reduction  of  camphenilone  by  sodium  and  alcohol  gives  camphenilol, 
the  corresponding  alcohol,  C9H17OH,  melting  at  84°. 

Camphor. 

The  essential  oil  derived  from  the  leaves  or  wood  of  Cinnamomum 
camphora 39  is  a  complex  mixture  from  which  camphor  is  more  or  less 
perfectly  separated  before  the  oil  comes  into  commercial  markets. 
According  to  Bertram  and  Wahlbaum 40  and  Schimmel  &  Co.  this 
essential  oil  contains,  in  addition  to  camphor,  pinene,  phellandrene, 
camphene,  dipentene,  dfenchene,  cUimonene,  bisabolene,  cineol,  safrol, 
eugenol,  terpineol,  citronellol,  borneol  and  cadinene.  Ordinarily  a 
light  terpene  fraction  is  separated  from  commercial  camphor  oil  as 
this  is  of  little  value,  and  the  heavier  oil,  containing  large  proportions 
of  safrol  and  eugenol,  constitutes  the  chief  commercial  source  of  safrol, 
employed  for  the  manufacture  of  piperonal.  In  addition  to  the  above 
named  constituents  Semmler  and  Rosenberg41  isolated  a  bicyclic 
sesquiterpene  boiling  at  129°-133°  at  8  mm.;  also  a  monocyclic  diter- 
pene,  C20H32,  which  they  have  named  ce-camphorene,  and  a  second 
diterpene  named  (3-camphorene  which  is  distinguished  from  the  a-hy- 
drocarbon  by  forming  a  liquid  hydrochloride.  So-called  camphoro- 
genol  reported  and  very  imperfectly  characterized  by  Yoshida,42  evi- 
dently does  not  exist. 

The  physical  properties  of  camphor,  as  recorded  in  the  literature, 
are  as  follows,  melting-point  1750,43  176.3°  to  176.50,44  178.4°  ;45 

"Parry  ("Chemistry  of  Essential  Oils,"  Ed.  3,  p.  160  [1918]),  has  called  atten- 
tion to  a  bulletin  issued  by  the  Monopoly  Bureau,  Formosa,  according  to  which  several 
varieties  or  species  (?)  of  camphor  trees  are  recognized  but  not  yet  distinguished 
botanically,  whose  essential  oils  do  not  yield  camphor. 

40  J.  prakt.  Chem.  (2)  49,  19  (1894). 

41  Ber.  46,  768   (1913). 

42  J.  Chem.  Soc.  Jftt  782    (1885)  ;  Cf.  Bertram  &  Wahlbaum,  loc  cit. 
«Landolt,  Ann.  189,  333  (1877)  ;  Beckmann,  Ann.  250,  353  (1889). 
"Foerster,  Ber.  23,  2983   (1890). 

"Haller,  Compt.  rend.  105,  229   (1887). 


BICYCLIC  NON-BENZENOID  HYDROCARBONS  467 

density  at  18°  0.9853 ;46  boiling-point  2040,43  209.1  ;44   [a]  D  44.22° 

in  20  per  cent  solution  in  alcohol.47  The  latent  heat  of  fusion 48  is 
8.23  calories  and  the  latent  heat  of  vaporization  is  93.4  calories. 

Identification  of  camphor  is  best  accomplished  by  preparing  the 
oxime49  melting-point  118°  to  119°.  As  pointed  out  by  Beckmann 
(loc.  cit.)  the  oxime  of  d.  camphor  is  Ia3vo-rotatory  and  the  oxime  of 
^.camphor  is  dextro-rotatory,  amounting  to  ±41.3°,  in  alcoholic  solu- 
tion. The  semicarbazone,  melting-point  236°-238°,  the  p-bromo- 
phenylhydrazone 50  melting  at  101°,  the  oxymethylene  derivative 
melting  at  80°-81°  and  the  benzylidene  compounds,  have  also  been 
employed  for  the  purpose  of  detecting  or  identifying  camphor.  The 
benzylidene  compound  of  inactive,  or  synthetic,  camphor  melts  at  78° 
but  that  of  d.  or  ^.camphor  melts  at  95°-96.°  Camphor  forms 
a  series  of  compounds  with  mercuric  iodide,51  C10H140.  Hg2I2; 
(C10H140)2Hg4I2;  (C10H140)4Hg5I2  and  (C10H140)3Hg6I2.  Nitric 
acid  forms  an  addition  product  C10H16O.HN03,  melting  at  24°,  and  the 
existence  of  a  second  compound  (C10H16O)2HN03,  melting  at  2.2°,  is 
indicated  by  the  freezing-point  curves.52  Hydriodic  acid  forms 
(C10H160)  .HI,  melting  at  29°-30°,  and  phosphoric  acid  forms  an 
addition  product  C10H16O.H3P04,  melting  at  29°. 

Neither  ordinary  camphor  nor  its  isomer  epicamphor  forms  a 
cyanohydrin.  Camphor,  menthone,  thujone  and  fenchone  do  not  react 
with  phenyl  hydrazine. 

The  Constitution  of  Camphor  and  Its  Oxidation  Products. 

The  study  of  the  constitution  of  camphor  and  its  oxidation  prod- 
ucts and  derived  substances  constitutes  a  brilliant  chapter  of  organic 
chemistry,  and  although  the  structure  of  camphor  has  been  known 
with  reasonable  certainty  for  some  time,  the  structures  of  some  of 
the  derived  oxidation  products  are  still  subjects  of  research.  Since 
this  collection  of  researches  is  such  a  classic  and  has  engaged  the 
attention  of  many  of  the  ablest  organic  chemists,  it  is  worth  while 

48  Cnautard,  Jahresber.  1863,  555  (for  Z.camphor)  ;  Malosse,  Compt.  rend.  154,  1697 
(1912),  gives  d^p-  0.963. 

47  Beckmann,  loc.  cit. 

"Jouniaux,  Bull.  soc.  chim.   (4)   11,  993   (1912). 
"Auwers,  Ber.  22,  605   (1889)  ;  Bredt,  Ann.  289,  6   (1896). 
MTiemann,  Ber.  28,  2191   (1895). 

61  Marsh  and  Struthers,  Proc.  Chem.  Soc.  24,  267   (1909). 

62  Shukoff  &  Kasatkin,  J.  Russ.  Phys.-Chem.  Soo.  41,  157   (1909). 


468       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

to  review  the  matter  somewhat  more  fully  than  some  other  related 
subjects.  For  the  sake  of  clearness  the  historical  method  of  review 
will  not  be  followed. 

In  the  earlier  work  undue  emphasis  was  put  upon  the  fact  that 
under  certain  conditions  camphor  could  be  converted  (with  very 
small  yields)  into  para-cymene,  also  to  carvacrol.  In  1893  Bredt53 
unraveled  the  structure  of  one  of  the  important  oxidation  products  of 
camphor,  i.e.,  camphoronic  acid.  On  heating,  camphoronic  acid 
breaks  up  into  carbon  dioxide,  isobutyric  acid  and  trimethyl  succinic 
acid,  a  change  which  Bredt  represented  as  follows: 

CH3 

H02C C CH2 :C02:H         — >    isobutyric  acid 

(a)  CH3  —  C  —  CH3 


C(XH. 


(b)  CH3  CH3 

|       :  CH3-CH-C02H 

H02C  —  C  — :  CH2  —  C02H    H02C  —  CH 

CH3  -  C  -  CH8' '  CH3  —  C  —  CH3  or  CH, 

|  |  >C-C02H 

C02H.  C02H          CH3 

camphoronic  acid  trimethylsuccinic  acid 

A  little  later  Bredt's  constitution  for  camphoronic  acid  was  conclu- 
sively confirmed  by  Perkin  and  Thorpe,54  who  made  the  acid  by  well- 
known  reactions  of  synthesis.  Bredt  represented  the  oxidation  of 
camphor,  through  camphoric  acid,  to  camphoronic  acid,  as  follows, 


C02H. 

camphoric  acid 


"Ann.  292,  55   (1896)  ;  Ber.  26,  3047   (1893). 
"J.  Chem.  800.  11,  1175   (1897). 


BICYCLIC  NON-BENZENOID  HYDROCARBONS 

CH,                                                          CH3 
CH, C CO.H  CH2 — C C02H 


469 


OH  camphononic  acid 

CH3 

CH2 C—     -C02H 

CH3  — C-CH3 

-I     C02H 
camphoronic  acid 

The  hydroxy  acid  shown  as  an  intermediate  product  in  the  above 
series  of  oxidations  is  usually  obtained  in  the  form  of  the  lactone, 
camphanic  acid, 

CH3 

f~*\  /"*1  /"\ 


CH 


—  C  — CH,    ,  0 


GEL 


The  correctness  of  Bredt's  constitution  for  camphoric  acid  is  very 
directly  shown  by  the  synthesis  of  this  acid,  first  by  Komppa  55  and 
later  by  Perkin  and  Thorpe.56  By  condensing  ethyl  oxalate  with 
pp-dimethylglutaric  ester,  by  means  of  sodium  ethoxide,  Komppa  ob- 
tained the  diethyl  ester  of  diketoapocamphoric  acid. 


C09R 


C02R  CO 


CH 


CO2R  CO 

"Ber.  34,  2472   (1901)  ;  S6,  4332    (1903). 
MJ.  Chem.  Soc.  89,  795   (1906). 


CH3—  C  —  CH3 
CH 


C09R 


C02R 


470       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

By  the  action  of  metallic  sodium  and  methyl  iodide  a  methyl  group 
was  introduced  and  the  two  ketone  groups  were  then  reduced,  first 
to  the  dihydroxy  acid,  then  by  hydriodic  acid  and  red  phosphorus 
to  the  unsaturated  acid  dehydrocamphoric  acid.  The  double  bond 
in  the  latter  acid  was  then  reduced  by  adding  HBr  and  reducing  the 
resulting  product  by  the  well-known  method  of  reduction  by  zinc 
dust  and  acetic  acid,  the  product  proving  to  be  racemic  camphoric 
acid. 


CO-       -CH C02R  CO C C02R 

CH3  —  C  —  CH3 
CO CH C09R 


dihydroxy  ]         (dehydrocamphoric 
acid  acid 


CH3 

CH2-       -C-       -C02H. 
CH3  — C  — CH3 

CH2 CH C02H 

r  —  camphoric  acid. 

Perkin  and  Thorpe's  synthesis  is  even  more  conclusive.57  Dimethyl- 
cyclopentanonecarboxylic  ester  was  treated  with  magnesium-methyl 
iodide  and  the  resulting  alcohol  converted  first  into  the  corresponding 
bromide  and  the  latter  into  the  nitrile,  which,  on  hydrolysis,  yields 
cU.camphoric  acid. 

"The  experimental  details  of  Komppa's  synthesis  were  published  several  years 
later  (Ann.  368,  126;  370,  209  [1909]).  Blanc  and  J.  C.  Thorpe  published  a  paper 
calling  in  question  the  structure  of  the  acid  obtained  by  methylating  diketoapocam- 
phoric  ester,  claiming  this  to  be  an  o-methyl  ether,  not  the  c-methyl  derivative  (J. 
Chem.  Soc.  97,  836  [1910]).  After  an  explanatory  reply  by  Komppa  (IMd.,  99,  29 
[1911]),  Blanc  and  Thorpe  admitted  their  error  (iUd.,  99,  2010  [1911]).  Komppa's 
synthesis  has  not  since  been  questioned. 


BICYCLIC  NON-BENZENOID  HYDROCARBONS  471 


-H2  -       -  CO 
CH3  —  C  - 
^TT                  PTT 

C 
-CH3        —  > 
.C02H                      C 

3 
T5~                                  f 

CH3 

HP 

OH 

CH3-C- 
HPJT 

CH3      -5 
CO  H 

CH 

^TT                    P 

CH3 

^H                C 

V^\_/2Xi 

PN 

CH3  —  C  —  CH3 
^TT                OTI             pn  TT               r 

CH3-C- 

CH3 
PO  P 

OXH. 


The  conversion  of  camphoric  acid  to  camphor  had  already  been 
effected  by  Haller.58  Camphoric  acid  forms  an  anhydride,  which  on 
reduction  by  sodium  amalgam,  yields  campholide, 

CO  CO 

C8H14<       >0        >        C8H14<       >0 

CO  CH2 

When  campholide  is  heated  with  potassium  cyanide  it  yields  a  nitrile 
which  on  hydrolysis  is  converted  into  homocamphoric  acid. 

CO  C02K  C02H 

C8H14<       >  0  +  KCN  -»  C8H14<  ->  C8H14< 

CH2  CH2CN  CH2.C02H. 

On  heating  the  calcium  salt  of  homocamphoric  acid,  Haller  obtained 
camphor. 

C02  C02 

C8H14<  >  Ca >  C8H14<  | 

CH2C02  CH2 

Dicarboxylic  acids  whose  carboxyl  groups  are  separated  by  two  or 
three  carbon  atoms  readily  yield  anhydrides,  as  in  the  case  of  succinic 

»Compt.  rend.  122,  446  (1896). 


472       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

and  glutaric  acids,  and  the  significance  of  the  formation  of  camphoric 
anhydride  was  first  pointed  out  by  Baeyer.59  Homocamphoric  acid, 
however,  does  not  form  an  anhydride,  indicating  that  the  two  carboxyl 
groups  are  separated  by  at  least  four,  carbon  atoms,  facts  which  agree 
with  Bredt's  constitution  and  the  syntheses  of  camphoric  acid,  noted 
above. 

Camphoric  acid  exists  in  a  form  which  does  not  yield  an  anhy- 
dride and  to  distinguish  this  form  it  has  been  called  isocamphoric 
acid.  Like  ordinary  camphoric  acid  the  iso  acid  exists  in  d.  and  I. 
and  a  racemic  form.  These  facts  also  harmonize  with  Bredt's  con- 
stitution for  camphor  and  the  chemical  evidence  as  to  the  structure 
of  camphoric  acid.  The  four  active  camphoric  acids  may  be  repre- 
sented as  follows, 


CH2  — C< 


CH3 
CO,H 


CH2  — C< 


CH2  —  C< 


C02H 


d.  and  I.  camphoric  acid 
CH, 


CH2  — C< 


CO,H 


CH2  —  C< 


CH2  — C< 


CH2  — C< 


H 


CH2  — C< 


C02H 
CH3 

*-6 

C02H 
H 

C02H 
CH3 

*6 

H 
COoH 


d.  and  I.  isocamphoric  acid 


In  camphor,  however,  the  two  carbon  atoms  represented  by  the  car- 
boxyl groups  in  the  camphoric  acids,  are  bound  to  each  other  and 
therefore  there  are  only  two  active  forms  of  camphor,  i.e.,  d.  and 
^.camphor,  corresponding  to  d.  and  ^.camphoric  acid.  In  camphor  the 
asymmetry  is  due  to  the  CO  group  and  optical  activity  disappears  if 


6*Ann.  276,  265.     Camphoric  anhydride  may   readily  be   prepared   by  heating   the 
acid  above  its  melting  point,  or  by  dehydrating  by  means  of  acetyl  chloride. 


B1CYCLIC  NON-BENZENOID  HYDROCARBONS  473 

this  ketone  group  is  reduced  to  CH2,  as  was  shown  experimentally  by 
Aschan.60 

Epicamphor,  or  (3- camphor.  It  will  be  evident  from  the  structure 
of  ordinary  camphor  that  another  isomeric  ketone  should  be  capable 
of  existence,  and,  in  accordance  with  the  nomenclature  suggested  for 
the  hydrocarbon  camphane,  ordinary  camphor  would  be  cc-camphor 
and  its  isomer  |3-camphor.  The  two  ketones  are  related  structurally 
to  each  other  as  follows, 


CH2 


ordinary,  or  a-camphor  Epicamphor,  or  ^-camphor 

In  the  conversion  of  camphor  to  epicamphor  a  reversal  of  the 
sign  of  optical  rotation  is  observed,  which  may  be  summarized  thus, 

d-camphor,   [a]  +  39.1°  ±5  ^-epicamphor,   [a]-Q — 58.2°. 

CO 

Hydroxymethylene  epicamphor,  C8H14<  |  ,  like  ordinary 

C  =  CHOH 

hydroxymethylene  camphor,  is  formed  when  Z.epicamphor  is  treated 
with  isoamyl  formate  and  sodium  in  the  presence  of  ether.61  It  ex- 
hibits muta -rotation,  increasing  on  standing,  particularly  in  the 
presence  of  sodium  ethylate;  freshly  prepared  material  showed 
[a]  - 125.5°  and  after  adding  a  trace  of  sodium  ethylate  the  rota- 

D 
tion  increased  to    [a]     — 146.7°.    The  decomposition  of   Z.epicam- 

D 

phoroxime  by  dilute  sulfuric  acid  proceeds  in  a  similar  manner  to  that 
of  camphoroxime,  forming  epicampholenonitrile,  with  rupture  of  the 
ring  as  in  ordinary  camphoroxime.  The  nitrile  may  be  hydrolyzed 
to  l.a-epicampholenic  acid,  but  the  behavior  of  this  acid  differs  from 
ordinary  a-campholenic  acid  in  not  rearranging  to  an  isomeric  acid 
corresponding  to  (3-campholenic  acid.  An  interesting  attempt  to  pre- 

80  Ann.  316,  229   (1901). 

61Perkin  &  Titley,  J.  Ctiem.  Soc.  119,  1090  (1921). 


474      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

pare  p-camphor  was  made  by  Haller  and  Blanc.62  Campholide,  made 
by  reduction  of  camphoric  anhydride,  yields  homocamphoric  acid  and 
camphor  as  follows, 

CO  C02K  C02H  CO 

C8H14<       >  0  ->  C8H14<  ->  C8H14<  ->  C8H14<  | 

CH2  CH2CN  CH2C02H  CH2 

Haller  and  Blanc  prepared  (3-campholide  but  this  substance  did  not 
react  with  potassium  cyanide.  Wagner63  believed  that  he  had  suc- 
ceeded in  preparing  p-borneol  by  applying  the  Bertram-Wahlbaum 
reaction  to  bornylene,  but  it  was  later  shown  that  his  bornylene  must 
have  been  very  impure  and  his  results  are  considerably  variant  from 
those  of  Perkin  and  Bredt.  Wagner's  method  was  carefully  tested  by 
Bredt  and  Hilbing,64  who  employed  a  very  pure  bornylene  and  a  mix- 
ture of  borneols  was  obtained  which  they  were  unable  to  separate 
and  on  oxidation,  ordinary  camphor  only  could  be  identified.  Epi- 
camphor  was  first  described  in  a  preliminary  paper  by  Perkin  and 
Lankshear65  and  almost  simultaneously  by  Bredt.66  However  much 
the  best  method  of  preparation  was  worked  out  by  Perkin  and  Bredt 
jointly,  their  method  consisting  in  treating  methyl  d-bornylene-3- 
carboxylate  67  with  hydroxylamine  in  the  presence  of  sodium  meth- 
oxide.  On  heating,  the  product  decomposes  forming  epicamphor,  the 
reactions  involved  probably  being  as  follows, 

C.C(OH)  z=N.OH  C-N:C  =  0  C.NH.CO,H 


C8H14<  ||  —  »  C8H14<  ||  --  >  C8H14< 

CH  CH  CH 

bornylene-3-hydroxamic 
acid 


C  —  NH2  C 

C8H14<  ||  -  >  C8H14<  |  —  >  C8H14<  | 

CH  CH2  CH2 

epicamphor 

Epicamphor  has  an  odor  similar  to  that  of  ordinary  camphor,  it 
melts  at  182°,  boils  at  213°;  its  oxime  melts  at  103°-104°  and  the 

*2Compt.  rend.  IJfl,  697    (1905). 
83  Her.  36,  4602    (1903). 
MJ.  prakt.  Chem.   (2)  84,  783   (1911). 
68  Proc.  Chem.  Soc.  27,  167   (1911). 
MChem.  Ztg.  35,  765   (1911). 

"Bredt,  Ann.  348,  200   (1906)  ;  366,  1    (1909)  ;  Bredt  &  Perkin,  J.  Chem.  Soc.  103, 
2182   (1913)  ;  Furness  &  Perkin,  J.  Chem.  Soc.  105,  2025   (1914). 


BICYCLIC  NON-BENZENOID  HYDROCARBONS  475 

semicarbazone  melts  at  237°-238°.  Sodium  and  alcohol  reduce  epi- 
camphor  to  the  corresponding  epiborneol,  melting-point  181°-182.5°. 
Like  ordinary  camphor,  the  new  ketone  does  not  react  with  hydrogen 
cyanide  and  is  not  reduced  by  zinc  dust  in  acetic  acid.  The  chemi- 
cal properties  of  epicamphor  do  not  differ  markedly  from  ordinary 
camphor  but  "favorable  action  of  epicamphor  on  the  beat  of  the  heart 
does  not  become  apparent  until  the  solution  administered  is  about 
four  times  stronger  than  that  which  produces  the  same  effect  in  the 
case  of  camphor." 

In  connection  with  the  discussion  of  the  constitution  of  camphor 
and  camphoric  acid  it  will  be  convenient  to  review  briefly  several 
related  derivatives.  The  nomenclature  in  this  series  of  acids  has 
been  very  much  confused  and  the  molecular  rearrangements  which 
some  of  them  undergo  made  the  determination  of  their  constitution  a 
matter  of  considerable  difficulty.  An  extension  of  our  knowledge  of 
the  pinacone-pinacoline  rearrangement  has  assisted  materially  in 
clearing  up  the  relationships  of  this  group  of  substances. 

Bredt68  has  reviewed  the  nomenclature  of  the  camphonene  and 
laurolene  series  and  suggests  abolishing  the  designations  "lauronolic 
acid"  and  "campholactone."  Two  series  of  unibasic  unsaturated  acids 
are  known  which  are  derived  from  camphoric  acid.  To  one  series 
belong  camphonenic  acid  and  lauronolic  acid  and  since  the  latter  acid 
is  unsaturated  it  may  more  appropriately  be  called  laurolenic  acid. 
Both  of  these  acids  contain  a  carbonyl  group  which  is  attached  to 
the  tertiary  carbon  atom  of  camphoric  acid.  In  the  other  series  the 
carbonyl  group  is  attached  to  the  secondary  position  and  includes 
campholytic  and  isocampholytic  acids  (|3-campholytic  acid).  It  is 
now  known  that  the  substances  formerly  known  as  lauronolic  and  iso- 
lauronolic  acids,  bihydrolaurolactone  and  isobihydrolaurolactone  are 
not  merely  differentiated  by  the  different  positions  of  the  double  bond, 
as  was  formerly  considered  to  be  the  case,  but  possess  different  carbon 
structures  since  camphonenic  acid  (below)  (iso  or  y-lauronolic  acid) 
still  contains  the  0era.dimethyl  group  of  camphoric  acid;  lauro- 
lenic acid  (formerly  lauronolic  acid)  does  not  possess  this 
group. 

For  the  purpose  of  a  key  for  reference,  the  revised  nomenclature 
suggested  by  Bredt  is  given,  as  follows. 

nJ.  prakt.  Chem.   (2)  87,  1   (1913). 


476       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 
I.    Camphonene  and  Camphonone  Series. 

CH3  CH3 

CH2-       -C-       -C02H.  CH2-       -C-       -C02H 

CH3  — C  — CH3  CH3  — C  — CH3 

5H2  =r=z=  C C02H.  CH2  =i==r  CH 

dehydrocamphoric  acid  camphonenic  acid. 

CH3                                                        CH3 
CH2 C C02H .  CH2 C C0,li 


CH3  —  C  —  CH3  CH3  — C  — CH3 

. CH2  CH2 CH.NH2 

camphonanic  acid.  aminocamphonanic  acid 

CH3  CH3 

CH2-       -C-    — C02H  CH2-       -C-       -CO 

CH3  — C  — CH3  |      CH3  — C  — CH3     0 

, CH.OH  CH2 CH^ 

camphonolic  acid  camphonololactone 

CH3 

CH2 C C02H. 

CH3  —  C  —  CH3 

camphononic  acid. 

II.   Laurolene  and  Laurolane  Series. 

CH3  CH3 

CH2-       -CH  CH2-       -C C02H 

C  — CH8  C  —  CH3 

C  —  CH3  CHo C CH, 


L2 

laurolene  laurolenic  acid 


BICYCLIC  NON-BENZENOID  HYDROCARBONS  477 

CH3  CH3 

CH2-      -C-      -C02H  CH2-      -C-      -C02H 

H  — C  — CH3  CH.CH3 

CH2 CH CH3  CH2 C  — 


CH, 


laurolanic  acid 


CH, 


laurololic  acid 


CH3 
CH, C CO 


CH.CEL  ^b 


laurololactone 


Some  of  the  synonyms  of  the  above  terms  are  as  follows: 

Synonym 


Bredt's  nomenclature 

Camphonolic  acid 
Laurololic  acid 
Camphonololactone 
Laurolanic  acid 

Laurololactone 

Laurolenic  acid 
Camphonenic  acid 


Hydroxylauronic  acid 

Hydroxy  acid  of  campholactone69 

Isocampholactone 70 

Dihydrolauronolic  acid 
fCampholactone 
iBihydrolaurolactone 

Lauronolic  acid 

y-lauronolic  acid 


Bredt 71  has  also  suggested  that  substituents  in  the  single  methyl  group 
of  camphoric  acid  be  designated  as  Q.  Bredt  follows  Kipping's  pro- 
posal that  substituents  in  the  0era.dimethyl  group  be  designated  by 
the  letter  it.  Thus  the  four  known  monobromocamphoric  acids  are, 

••Noyes,  J.  Am.  Chem.  Soc.  34,  182  (1912). 
™Noyes.  J.  Am.  Chem.  Soc.  Slt  278  (1909). 
"Ann.  335,  26  (1913). 


478       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


CH3 


C(XH 


C09H 


H 


CH 


—  C  — 


CH 


>C 


-COaH 


Br 

S-Bromocamphoric  acid 

CH3 
CH9 C C02H 


4-Bromocamphoric  acid 

CH2Br 
CH2 C C02H 


CH3  —  C  —  CH2Br 

C C02H 

H 

n-Bromocamphoric  acid 72 


CH, 


CH3  —  C  —  CH3 

C 

H 

Q-Bromocamphoric  acid 


C09H 


From  chlorocamphoric  phenyl  ester  by  heating  with  quinoline, 
saponifying  the  resulting  unsaturated  ester  and  heating  the  free  acid, 
Bredt 74  obtained  an  acid  whose  structure  he  represented  as  follows, 

CH3 


CH, 


CH, 


CH3 
C 

-i- 

-A- 


C09R 


CH, 


C02R 


CH, 


\ 


C02R 


CH3  —  C  —  CH3 
CH C02R 


Cl 


CH  ===CH 


camphonenic  acid 

"Kipping,  J.  Chem.  8oc.  69,  918   (1896). 

"Armstrong  &  Lowry,  J.  Chem.  Soc.  81,  1467   (1902). 

7*5er.  35,  1286  (1902).  This  acid  was  originally  termed  "lauronolic  acid"  by 
Bredt,  but  later  changed  to  camphonenic  acid  to  avoid  confusion  with  Fittig  and 
Woringer's  lauronolic  acid.  Cf.  W.  A.  Noyes  &  Burke,  J.  Am.  Chem.  Soc.  3li,  177 
(1912).  In  a  later  paper  by  Bredt  [Ann.  895,  26  (1913)]  d.dehydrocarnphoric  acid, 
melting-point  202°-203°,  and  tU.dehydrocamphoric  acid,  melting-point  228°,  is  described. 


BICYCLIC  NON-BENZENOID  HYDROCARBONS  479 

Bredt  arriveji  at  this  structure  from  the  fact  that  the  acid  gives 
camphoronic  acid  on  oxidation. 

CH3  CH3 

CH2-       -C-       -C02H  CH2-       -C-       -C02H 

CH  CH  C02H  C02H 

Camphoronic  acid 

Camphononic  acid  is  one  of  the  important  members  of  this  series. 
On  further  oxidation  it  yields  camphoronic  acid 75  and  its  constitution 
is  as  shown  in  the  following, 

CH3  CH3 

C C09H  CH2-       -C C02H 

CH3  — C  — CH3 

:02H          C02H 

camphononic  acid 

By  oxidizing  dibromocamphor  by  dilute  nitric  acid  and  silver  nitrate 
Lapworth  and  Chapman75  obtained  homocamphoronic  acid,  whose 
anhydride  loses  C02  yielding  camphononic  acid. 

CHa  CH3 

C02H        CH2-       -C-       -C02H 

CH3  — C  — CH3    +C02+H20 


COOH         OH 

Lapworth  and  Lenton76  also  made  camphononic  acid  in  two  other 
ways  which  also  indicate  the  constitution  shown.  The  amide  of  cam- 
phanic  acid  was  converted  by  dehydration  to  the  nitrile  and  this,  on 
treating  with  concentrated  alkali  loses  HCN  to  give  camphononic  acid. 
Their  second  method  also  starts  with  camphanic  acid  amide;  by  treat- 
ing with  bromine  and  caustic  soda  the  CONH2  group  is  replaced  by 

"Lapworth  and  Chapman,  J.  Chem.  Soc.  75.  986   (1899). 
nJ.  Chem.  Soc.  79,  1284  (1901). 


480       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


NH2  and  the  resulting  product  decomposes  yielding  ammonia  and 
camphononic  acid. 

CH3  CH3 

C CO  CH2 C 

\ 


COaK 


CHq  — C  — CH3    O  -*nitrile 


CH, 


C 


CHQ  — C  — CH 


CONH,  CH 


C< 


OH 

CN 


CH3 

CH2 C C02H 

CH3  —  C  —  CH3 


camphanic  acid  amide 

* 
CH3 

CH2 C-      -C02H 

CH3  —  C  —  CH3 

i<°H 

NH2 

When  camphononic  acid  is  reduced  electrolytically  the  ketone 
group  is  reduced  without  structural  change,  to  give  camphonolic  acid 
or  its  lactone.77 

CH3  CH3 

, C COCH  CH2 —  C COOH 

CH3  — C  — CH3  -*       |      CH3  — C  — CH3  > 

CH2 C==0  CH2 CH.OH 

camphonolic  acid 
cis.  trans.  M.-P.  2^9° 
CH3 

—  C  — 


CH. 


CH, 


CH2 


CO 

CH,  —  C  —  CH3     0 
/ 


H  — 


lactone  M.-P.  160° 

"Bredt,  J.  praU.  Chem.  (2)  84,  786   (1911)  ;  Ann.  366,  I   (1909). 


BICYCLIC  NON-BENZENOID  HYDROCARBONS 


481 


It  will  have  been  noted  that  the  above  substances  retain  the  carbon 
structure  of  camphoric  acid.  Fittig  and  Woringer78  had  obtained  an 
acid  by  the  decomposition  of  bromocamphoric  anhydride  which  they 
had  termed  lauronolic  acid  but  since  it  did  not  give  the  oxidation 
products  described  above  many  chemists  refused  to  accept  Bredt's  pro- 
posed constitution  of  camphoric  acid.  Fittig  and  Woringer's  lauro- 
nolic acid  does  not  give  camphoronic  acid  on  oxidation.  What  ap- 
pears to  be  the  correct  explanation  of  the  structure  of  this  acid  was 
given  by  Lapworth  and  Lenton79  and  also  confirmed  by  other  evi- 
dence. In  the  preparation  of  Fittig  and  Woringer's  lauronolic  acid 
by  the  decomposition  of  camphanic  acid,  Lapworth  and  Lenton  assume 
a  structural  rearrangement  similar  to  the  change  of  position  of  a 
methyl  group  in  the  pinacone — pinacoline  rearrangement.  Accord- 
ingly, Fittig  and  Woringer's  lauronolic  acid  has  the  structure  shown 
in  the  following. 

CH3  CH3 

C CO  CH9 C  — 


CH, 


-CO 
\ 


CO 


CH3  —  C  —  CH3 


\ 


0 


CH 


C 


C0H 


camphanic  acid 
CH3 

CH2-       -C-       -C02H 
CH,  —  C  —  H 


Laurolenic  acid  (Bredt). 
(lauronolic  acid) 


\ 


CH3 

This  lactone  proves,  in  fact,  to  be  different  from  the  lactone  of 
camphonolic  acid  later  made  by  Bredt.  In  the  light  of  the  fore- 
going, other  facts  become  clear,  for  example  the  oxidation  of  lauro- 
nolic acid  by  potassium  permanganate 80  to  laurenone. 

"Ann.  227,  6    (1885). 

"  Loc.  cit. 

««Tiemann  &  Tigges,  Ber.  S3,  2950   (1900). 


482      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

CH2 

CO  — CH3 


CH5 


or 


GIL 
CH, 


CHu 

AH 


C-CIL 


CO 


-i 


H 


Also  the  nitro  derivative  and  its  reaction  products,  obtained  by 
Schryver81  are,  according  to  Bredt,  also  in  harmony  with  the  other 
known  facts,  the  nitro  group  displacing  the  tertiary  hydrogen,  as  is 
customary,  Schryver's  nitro  derivative  probably  having  the  struc- 
ture, 

CH8 

CH2- 0 


Oxidation  to  camphoronic  acid  is  therefore  the  criterion  as  to  whether 
or  not  the  C  (CH3)  2  group  of  camphoric  acid  is  retained,  and  as  sur- 
mised by  Lapworth  and  Lenton,  Fittig  and  Woringer's  lauronolic  acid 
and  its  derived  lactone  (bihydrolaurolactone)  and  the  hydrocarbon 
laurolene,  do  not  possess  this  structure. 

A  similar  rearrangement  of  a  methyl  group  occurs  in  the  conver- 
sion of  campholytic  acid  to  isocampholytic  acid.82 . 

« J.  Chem.  Soc.  73,  559  (1898). 

M  This  name  has  been  agreed  to  by  Noyes,  Perkin,  Aschan  and  Bredt  to  replace 
the  various  other  names  by  which  it  has  been  known,  e.  g.,  isolaurolonic,  camphothetic, 
and  ^-campholytic  acid. 


BICYCLIC  NON-BENZENOID  HYDROCARBONS  483 

CH3  CH3 

CH  _  C  CH2; C CH3 

CH3-C-CH3  »  I  C-CH3 

CH2-       -CH-       -C02H  CH2 C C02H. 

campholytic  acid.  isocampholytic  acid. 

In  connection  with  the  relationships  just  discussed  it  will  be  con- 
venient to  mention  the  work  indicating  the  structure  of  laurolene  and 
isolaurolene  C8H14.  Isolaurolene  has  been  obtained  by  heating  copper 
camphorate  and  also  from  isocampholytic  acid  ((3-campholytic  acid). 
Its  structure  has  been  determined  by  Blanc  83  by  a  study  of  its  oxida- 
tion products  and  confirmed  by  it*  synthesis,  to  be  1 . 1 . 2-trimethyl- 
A2-cyclopentene. 


isolaurolene 
CH2 

Noyes  and  Derick84  prepared  laurolene  by  treating  aminolauronic 
hydrochloride  with  sodium  nitrite,  also  by  boiling  the  nitroso  deriva- 
tive of  aminolauronic  anhydride  with  caustic  soda.  They  found 
experimental  evidence  which  they  considered  as  supporting  the  struc- 
ture which  Eijkmann 85  had  proposed  on  the  ground  of  refractometric 
considerations.  Noyes  and  Kyriakides86  made  the  hydrocarbon  by 
simple  methods  of  synthesis  which  confirm  the  structure  proposed  by 
Eijkmann,  i.e., 

CH, 


laurolene 


M  BuU.  sac.  chim.   (3)  19,  703. 

"J.  Am.  Chem.  8oc.  SI,  669  (1909). 

MChem.  Zentr.  1907,  II,  1208. 

"J.  Am.  Chem.  Soc.  52,  1064   (1910). 


484      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 
The  physical  properties  of  the  laurolenes  are  as  follows:  dlaurolene, 

[a] 26.2°^   ,  2815o.  d^=  0.8030;  boiling-point  120.3°-121°.    Iso- 

D  4° 

laurolene  boils  at  108°. 

Derivatives  of  Camphor. 

Camphor  Oxime  87  is  readily  made  in  good  yields  by  adding  the 
calculated  quantity  of  concentrated  caustic  soda  to  an  alcoholic  solu- 
tion of  camphor  and  hydroxylamine  hydrochloride  and  heating  on  a 
water  bath  for  about  one  hour.  The  oxime  crystallizes  well  from 
dilute  alcohol,  melting-point  120°.  It  boils  at  249°-250°  with  very 
slight  decomposition.  Camphor  oxime  is  reduced  by  hydrogen  and 
catalytic  nickel  at  180°-200°  to  bornylamine,  dibornylamine  and 
camphylamine,  the  second  being  the  principal  product.88 

C  =  N.OH 

Isonitrosocamphor,  C8H14<|  exists  in  two  forms,  melt- 

CO 

ing  at  114°  and  1530.89  For  its  preparation90  102  grams  of  camphor 
are  dissolved  in  500  cc.  of  dry  ether  and  15.2  grams  of  sodium  as 
sodium  wire,  are  added.  Amyl  nitrite  is  then  added  in  small  portions 
with  cooling,  until  78  grams  have  been  added.  After  standing  about 
three  hours,  add  cracked  ice  and  ice  water;  the  sodium  salt  of  isonitroso 
camphor  is  in  the  aqueous  phase  and  unchanged  camphor  and  borneol 
in  the  ether.  Acetic  acid  precipitates  the  free  isonitroso  derivative, 
which  after  recrystallizing  from  dilute  methyl  alcohol,  or  petroleum 
ether,  melts  at  152°-154°. 

Zinc    and    dilute    acids    readily    reduce    it    to    amido    camphor 

CH.NH2 
C8H14<|  boiling-point    244°,    whose    hydrochloride    has    a 

physiological  action  similar  to  curare,  but  feebler.  Two  molecules  of 
amidocamphor  may  be  condensed  to  dihydrocamphenepyrazine.91 
Amidocamphor  and  potassium  cyanate  yield  camphorylcarbamide 

CH.NHCONH2 
C8H14<|  which  may  be  converted  to  camphoryliso- 

cyanate  by  the  action  of  nitrous  acid.    Like  the  well-known  reagent, 

"Auwers,  Ber.  22,  605    (1889). 

"Aloy  &  Brustier,  Bull.  soc.  chim.   (4)   9,  733    (1911). 

"Chem.  Zentr.  1908,  I,  1270. 

•°Claisen  &  Manasse,  Ann.  271,  73   (1893). 

« Ann.  313,  25    (1900). 


BICYCL1C  NON-BENZENOID  HYDROCARBONS  485 

phenylisocyanate,  the  camphoryl  derivative  is  very  reactive  and  a 
large  number  of  camphorylurethanes  and  other  derivatives  have  been 
prepared  from  it.92  When  amidocamphor  hydrochloride  is  treated 

C=Na 
with  nitrous  acid,  azocamphor,  C8H14<|  is  produced.93 

CO 
CO 
Camphor  Quinone,  C8H14<|      .  When  isonitrosocamphor  is  heated 

CO 

with  dilute  sulfuric  acid,  the  diketone  is  formed,  as  in  the  hydrolytic 
decomposition  of  oximes, 

C  =  N.OH  CO 

(a)  C8H14<   |  +H,0-^C8H14<   |       +H2N.OH 

CO  CO 

C  =  N.OH  CO 

(b)  C8H14<   |  +NO.OH  ->  C8H14<   |       +N20  +  H,0 

CO 


Nitrous  acid  also  converts  isonitrosocamphor  to  camphorquinone.94 
About  9  parts  of  camphor  are  dissolved  in  15  parts  acetic  acid  and 
4  parts  sodium  nitrite  (dissolved  in  minimum  of  water)  are  carefully 
added.  After  completion  of  the  reaction  the  diketone  is  precipitated 
by  diluting  with  cold  water.  The  diketone  is  easily  volatile,  crystal- 
lizes well  in  yellow  needles  melting  at  198°,  and  is  markedly  soluble 
in  hot  water. 

The  effect  of  the  two  contiguous  CO  groups  upon  the  stability  of 
the  ring  is  noteworthy,  the  diketone  being  easily  converted  to  cam- 
phoric acid  or  its  derivatives  under  the  influence  of  a  wide  variety  of 


reagents.95    The  dioxime,  C8H14<|  is  best  made  by  the 

C  =  N.OH 

action  of  hydroxylamine  on  isonitroso-camphor.  All  of  the  eight  pos- 
sible oximino  derivatives  of  camphorquinone  are  known.  The  dis- 
covery of  the  two  modifications  of  isonitrosoepzcamphor,  constituting 
the  third  and  fourth  monoximes  of  camphor  quinone,  completes  the 
list  of  theoretically  possible  oximes  and  Forster  96  has  shown  the  prob- 
able configuration  of  these  derivatives.  Their  physical  properties  are 
as  follows, 

"Chem.  Zentr.  1908,  I,  257. 
"Angeli,  Ber.  26,  1718   (1893). 

•*Claisen  &  Manasse,  Ann.  27-k  83  (1893)  ;  Lapworth,  J.  CTiem.  Soc.  69,  322  (1896)  ; 
Bredt,  Rochussen  &  Monheim,  Ann.  S14,  388   (1900). 
88Aschan,  Ber.  SO,  657,  659   (1897). 
*  J.  Chem.  Soc.  103,  662   (1913). 


486      CHEMISTRY  OF  THE  NON-BENZEN01D  HYDROCARBONS 


Melting- 
Point 
114° 

in 
Chloroform 
172.9° 

in 
2%  NaOH 
275.3° 

Isonitrosocamphor  (stable)       

152° 

197.0° 

288.0° 

Isonitrosoepicamphor    (unstable)          • 

137° 

-179.4° 

-278.5° 

Isonitrosoepicaniphor  (stable)            . 

.   ..        170° 

-200.1° 

-422.0° 

CainpliorQuiiioDe    (x~dioxiiii6 

201° 

-51.7° 

-103.8° 

CamphorQuinonG     3-dioxim6 

248° 

-24.5° 

136° 

16.4° 

14.3° 

Camohorauinone.   fi-dioxime    . 

194° 

52.8° 

87.0° 

Reduction  of  the  diketone  by  zinc  dust  and  acetic  acid  gives  a-oxy- 

CH.OH 

camphor  C8H14<|  melting-point  203°-205°.   Sodium  and  alco- 

CO 

CH.OH 
hoi    causes    further    reduction    to    camphorglycol,    C8H14<| 

CH.OH 

melting  at  231°.  This  glycol  may  be  regarded  as  bornyleneglycol 
and  is  not  identical  with  the  glycol  of  camphene.  Camphor-quinone 
undergoes  condensation  with  nitromethane  very  readily  and  nitrome- 
thylenecamphor  and  the  intermediate  product,  nitromethylhydroxy- 
camphor,  have  been  isolated.97 


CO 
C8H14<   | 

CO 


C(OH).CH2N02 
C8H14<   | 

CO 


C8H14  < 


Condensation  with  ethyl  cyanoacetate  also  readily  takes  place  yield- 

C02Eth 


ing  ethyl  camphorylidene-cyanoacetate,    C8H14< 


| 
CO 


CN 


from  which  the  corresponding  camphorylidenemalonic  acid  was  ob- 
tained. 

Para-diketocamphane:  When  a  mixture  of  bornyl  and  isobornyl 
acetates  are  oxidized,  in  glacial  acetic  acid,  by  chromic  acid,  an 
acetoxy  camphor  is  produced,98  and  since  pure  .isobornyl  acetate  does 
not  give  this  result,  this  derivative  must  be  a  product  resulting  from 

•'Forster  &  Withers,  J.  Chem.  Soc.  101,  1328   (1912). 
"SchrOtter,  Monatsh.  1881,  224. 


BICYCLIC  NON-BENZENOID  HYDROCARBONS  487 

the  oxidation  of  bornyl  acetate.  Hydrolysis  of  the  acetate  gives 
hydroxy camphor,  melting  at  238°-246°,  this  product  really  consisting 
of  two  stereoisomerides.  Oxidation  of  hydroxycamphor  by  chromic 
acid  gives  para-diketocamphane,  melting-point  206.5°-207°  and 

13  5° 

Bredt "  finds  that  the  diketone  is  optically  active,  [a]  — _  +  103.42°. 

Since  this  substance  is  not  identical  with  camphorquinone  and  since 
a  substance  in  which  both  CO  groups  were  attached  to  the  same 
bridge  carbon  atom  would  be  optically  inactive,  Bredt  concludes 
that  the  constitution  of  the  two  substances  are  as  indicated  below. 


=  0  CH2  -  C  -  C  =  0 

H 
Para-  dik  e  tocamphane 

The  relative  ease  with  which  camphor  reacts  with  metallic  sodium 
or  sodium  amide  to  form  a  sodium  derivative,  has  been  made  use  of 
extensively  for  the  preparation  of  other  derivatives.  Thus,  sodium 
camphor  in  benzene  solution  reacts  with  C02  to  give  d.camphocarbonic 

CH.C02H 
acid,  C8H14<|  ,  melting  at  128°.    A  recent  synthesis  of  cam- 

phocarbonic  acid  by  Ruzicka  10°  is  worth  noting  since  a  well-known 
reaction  was  successfully  applied  to  this  synthesis  by  the  simple 
expedient  of  employing  an  autoclave  to  obtain  a  temperature  of  200°. 
The  diethyl  ester  of  homocamphoric  acid  was  condensed  by  sodium 
ethylate  in  alcohol  at  200°. 

CO^  CO 

C8H14  <  '  C8H14 


CH2C0R  CH.C0R 


| 
CH. 


Camphocarbonic  acid  has  been  employed  for  the  preparation  of  pure 
bornylene.  The  a-hydrogen  atom  in  camphocarbonic  esters  is  readily 
displaced  by  sodium,  by  which  means  alkylation  is  easily  effected; 
alkyl  halides  give  C-derivatives  but  acid  chlorides  give  o-acylated 


WJ.  prakt.  Chem.    (2)   101,  273   (1920). 
100Helv.  Chim.  Acta.  S,  748   (1920). 


488      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

C.C02R  CH.CN 

products,  C8H14<  1 1  .    The  closely  related  nitrile  C8H14<| 

C.OAc  CO 

also  forms  a  monosodium  derivative  which,  by  the  action  of  alkyl 
iodides,  yields  a  mixture  of  0  and  C  alkyl  derivatives. 

Camphocarbonic  acid  and  its  alkyl  derivatives  readily  decompose 
on  heating,  a  molecule  of  carbon  dioxide  and  camphor  or  a  derivative 

CHR 
C8H14<|         being  formed.    The  introduction  of  a  methyl  group  in 

CO 
this  case  has  a  very  marked  effect  upon  the  melting-point,  methyl- 

CH.CH3 
camphor  C8H14<|  melting  at  38°;  ethylcamphor  and  dime- 

thylcamphor  are  liquids,  their  odor  being  suggestive  of  menthone 

rather  than  camphor. 

C  =  CH.OH 
Oxymethylenecamphor,    C8H14<|  is    of    interest    on 

C  =  0 

account  of  its  strongly  acidic  character.  It  is  prepared  by  the  action 
of  methyl  or  ethyl  formate  on  sodium  camphor  or  magnesium-camphpr 
bromide,  or  by  the  action  of  sodium  methoxide  on  a-mono-halogen 
or  a-dihalogen  camphor.101  As  in  similar  "formyl"  derivatives  some 
reactions  indicate  the  structure  indicated  above  and  other  reactions 

CH.CHO 
point  to  the  desmotropic  form,  C8H14<|  '.    It  readily  forms 

an  acetate  and  a  series  of  ethers;  it  combines  with  nascent  hydro- 
cyanic acid  to  give  a  cyanhydrine  and  is  reduced  by  sodium  and 

CH.CH2OH 
alcohol  to  camphylglycol,  C8H14<|  ,  which  is  known  in  two 

CHOH 

forms,  cis  melting  at  87°  and  trans  melting  at  118°.  The  trans- 
glycol  is  oxidized  by  potassium  permanganate  to  £rans-borneolcarbonic 

CH.C02H 
acid  C8H14<|  but  cis-borneolcarbonic  acid  is  unstable  and 

CHOH 
oxidation  in  this  case  proceeds  to  camphoric  acid.102 

CH.CH2OH 
Reduction  of  camphylcarbinol  C8H14<|  by  sodium 

/^TT 

<^±i2 

101Brtihl,  Ber.  37,  2069    (1904). 
1MBredt,  Ann.  S66,  62   (1909). 


BICYCLIC  NON-BENZENOID  HYDROCARBONS  489 

in    moist    benzene    or    condensation    of    camphylbromomethane    by 

CHCH2  — CH2CH 

sodium,103  gives  dicamphylethane,  C8H14<|  >C8H14, 

CH2  CH2 

melting-point  209°-211°. 

Reduction  of  camphor  by  passing  over  catalytic  nickel  and 
alumina  at  200°  gives  isocamphane,104  melting-point  64.5°,  boil- 
ing-point 164°-165°.  Camphor  condenses  with  oxalic  ester,105 
under  the  influence  of  sodium  ethylate,  to  camphoroxalic  acid 

CH.COC02H 

C8H14<|  melting-point  88°,  which  has  yielded  a  series 

CO 

of  derivatives.  The  above  reactions  will  serve  to  make  clear  the 
very  marked  reactivity  of  the  CH2  group  contiguous  to  the  ketone 
group  in  camphor.  ^ 

Camphoric  Acid  has  been  discussed  above  on  account  of  the  im- 
portance of  its  constitution  to  that  of  camphor  itself.  Its  preparation 
is  not  difficult  and  the  original  method  of  Wreden 106  gives  quite  satis- 
factory yields.  To  300  grams  of  camphor  3  liters  of  nitric  acid,  Sp. 
Gr.  1.27,  are  added  and  the  mixture  warmed  on  a  water  bath  for 
several  days.  When  cold  the  crude  crystals  are  taken  up  in  about 
1  liter  of  water  and  milk  of  lime  made  from  50  grams  of  lime  are 
added,  which  forms  the  freely  soluble  acid  salt.  The  soluble  salt  is 
separated  from  unchanged  camphor  and  the  camphoric  acid  is  then 
precipitated  with  more  milk  of  lime  as  the  sparingly  soluble  neutral 
salt,  from  which  the  acid  may  be  liberated  by  hydrochloric  acid; 
yield  about  250  grams,  melting-point  178°.  It  is  soluble  in  160  parts 
of  water  at  12°  but  is  soluble  in  10  to  12  parts  of  water  at  100°.  In-  j 
active  (d.l.)  or  para-camphoric  acid  melts  at  204°. 

On  heating  calcium  camphorate  the  expected  ketone  formation  \ 
takes  place  but  the  bridged  ring  is  also  broken,  the  constitution  of  the 
resulting  product,  camphorphorone,  having  been  shown  by  a  study 
of  its  oxidation  products  and  its  synthesis  from  2-methyl  cyclopen- 
tanone  and  acetone  (by  condensing  by  sodium  ethoxide)  and  the 
hydrolytic  decomposition  of  camphorone  by  caustic  alkali  to  this 
ketone  and  acetone.107  The  latter  reaction  will  recall  the  similar 

103Rupe  &  Ackermann,  Helv.  Chim.  Act'a.  2,  221    (1919). 

10*Ipatiev,  Ber.  tf,  3205    (1912). 

ios  Tingle,  J.  Am.  Cnem.  Soc.  2J,  363   (1901)  :  29.  277    (1907), 

106  Ann.  163,  323    (1872). 

""Wallach,  Ann.  331,  322    (1904), 


490       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

behavior  of  citral,  pulegone  and  other  substances  which  possess  the 
group  (CH8)2C  = 


c 

^TT                  ( 

;HS 

•«               CO 

?H'H 

CH                C  ^ 

CH3  —  ( 

1 
^H             C 

}_CH3            Ca  - 
H           CO 

->                            CO 
CH               C 

C 
~^H               C 

% 

^                            CH  - 

CH3  —  C  —  CH3 
CH3 

c-H 

^TT                 C, 

CO        ±5 
CH 

CO+(CH3)2CO 

..ii 

H, 

CH3  — C  — CH3 

When  camphorphorone  is  reduced  by  hydrogen  over  catalytic 
nickel 108  at  130°  the  saturated  ketone,  dihydrocamphorphorone,  is 
produced,  which  on  reduction  at  a  higher  temperature,  280°,  is  further 
reduced  to  l-methyl-3-isopropylcyclopentane  (boiling-point  132°- 
134°). 


CH, CH  C3H7 


Camphorimide,  melting-point  243°,  is  readily  made  when  dry  am- 
monia is  passed  into  boiling  camphoric  acid.109 

Camphor  reacts  normally   with   magnesium-allyl   bromide110   to 

C(OH).CH2CH  =  CH2 

give  allyl  borneol,  C8H14<|  which  on  oxida- 

CH2 

:°8Godchot  &  Taboury,  Bull.  soc.  cMm.   (4)   IS,  599   (1913). 

109  Evans,  J.  Chem.  Soc.  97,  2237   (1910). 

ll°Khoin,  J.  Ruaa.  Phys.-Chem.   Soc.  kk,  1844    (1912). 


BICYCLIC  NON-BENZENOID  HYDROCARBONS  491 

C(OH).CH2C02H. 

tion  by  permanganate  yields  the  acid  C8H14<| 

CH2 

Haller  has  shown  that  by  the  action  of  alkyl  halides  and  sodium 
amide,  camphor  may  be  alkylated,  the  substitution  in  such  ketones 
replacing  one  or  more  hydrogen  atoms  adj  acent  to  the  carbonyl  group. 
Haller111  has  thus  prepared  dimethyl,  methylethyl,  propyl,  dipropyl, 
benzyl,  dibenzyl  and  ethylbenzyl  camphors.  By  reduction  of  these 
ketones  the  diethyl,  methylethyl,  propyl  and  dibenzylborneols  were 
obtained. 

The  quantitative  determination  of  camphor  in  commercial  prod- 
ucts such  as  celluloid  or  spirits  of  camphor  is  somewhat  difficult  on 
account  of  its  volatile  character.  It  can  be  precipitated  from  alco- 
holic solutions  by  concentrated  aqueous  calcium  chloride,112  taken  up 
in  light  petroleum  ether  and  finally  determined  gravimetrically.  In 
the  case  of  celluloid,  distillation  of  the  finely  rasped  product  with 
steam  gives  fairly  satisfactory  results,113  if  no  camphor  substitutes  are 
present.  Extraction  of  rasped  celluloid  for  10  hours  with  petroleum 
ether  also  gives  good  results.  The  use  of  an  immersion  refractometer 
on  solutions  of  camphor  in  methyl  alcohol  has  also  been  employed.11* 

Homocamphor:  This  ketone  closely  resembles  ordinary  camphor 
in  its  physical  properties  and  chemical  reactions.  It  is  a  white  crys- 
talline substance  melting  at  189°-190°,  sublimes  easily  and  has  an 
odor  closely  resembling  ordinary  camphor.  It  has  one  more  CH2 
group,  in  the  ring  containing  the  CO  group,  than  ordinary  camphor. 
It  has  recently  been  made  115  from  camphoric  acid  anhydride  by  con- 
densing with  diethyl  sodio-malonate,  reducing  the  product  thus  ob- 
tained and  on  distilling  the  resulting  acid  hydrocamphorylmalonic 
acid  is  obtained, 

CO  C  =  C(C02C2H5)2 

C8H14  <       >  0  >  C8H14  <       >  0  » 

CO  CO 

C02H 
CH2CH<  CH2.CH2OXH 

C.H14<  C02H »C8H14<  > 

C02H  C02H 

hydrocamphorylacetic  acid. 

»"  Haller  &  Bauer,  Compt.  rend.  158,  754  (1914)  ;  Haller  &  Louvrier,  Compt.  rend. 
148f  1643    (1909) . 

naPenniman  &  Randall,  J.  Jnd.  d  Eng.  Chem.  6,  926. 
118  Barthelemy,  Kunstoffe,  3,  46  (1913). 

>«Utz,  Chem.  Abs.  I,  1467   (1907)  ;  Arnost,  Z.  Nahr.  Oenussm.  12,  532. 
"•Lapworth  &  Royle,  J.  Chem.  Soc.  117,  744  (1920). 


492       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

CH2CH2 

>  C8H14  <    / 

CO 

Heating  the  lead  salt  of  the  last  named  acid  or  prolonged  heating  with 
acetic  anhydride  yields  homocamphor. 

Synthetic  Camphor 

The  economic  balance  between  the  cost  of  manufacturing  camphor 
synthetically  and  obtaining  it  from  natural  sources  is  at  present  com- 
paratively even,  and  success  in  the  manufacture  of  synthetic  camphor 
is  very  largely  determined  by  factors  over  which  the  manufacturing 
chemist  has  no  control.  The  development  of  this  industry  was  coin- 
cident with  the  very  great  rise  in  price  of  natural  camphor  after 
Japan  had  succeeded  in  practically  monopolizing  the  production,  of; 
natural  camphor.  The  large  tree  Cinnamomum  camphora  is  the  only 
commercial  source  of  natural  camphor  and  the  production  of  camphor, 
by  steam  distilling  the  chipped  wood  of  large  mature  trees  of  sixty 
years  or  more  in  age,  has  been  carried  out  in  China  and  Japan  for 
several  hundred  years.  True  camphor  was  known  in  Europe  at  least 
as  early  as  1583,  but  owing  to  the  custom  of  cutting  down  the  trees 
for  distillation  of  the  wood,  together  with  the  increased  demands  for 
camphor  resulting  from  the  development  of  the  celluloid  industry, 
large  mature  trees  became  more  and  more  scarce  in  Japan  and  North 
Central  China,116  with  the  result  that  in  1903  the  industry  in  Japan 
was  made  a  Government  monopoly.  Camphor  had  been  produced  in 
Formosa,  coming  into  the  market  prior  to  1895  as  Chinese  camphor, 
but  after  this  island  was  acquired  by  Japan,  camphor  production  was 
vigorously  pushed  by  the  Japanese  and  Formosa  soon  became  the 
principal  producing  locality.  With  the  elucidation  of  the  constitution 
of  camphor  and  related  substances,  its  artificial  production  was  prac- 
tically certain  to  be  undertaken,  but  this  was  greatly  stimulated  by 
the  attempted  price  manipulation  of  the  Japanese  monopoly.  Cellu- 
loid, the  manufacture  of  which  was  first  developed  by  John  W.  Hyatt 
of  Newark,  N.  J.,  is  the  chief  industrial  use  of  camphor,  this  industry 
consuming  seventy  to  eighty  per  cent  of  the  world's  total  camphor 
production.  The  recent  rapid  development  of  the  moving  picture 
industry  has  added  to  the  consumption  of  camphor  for  the  manu- 
facture of  films  and  a  further  consumption  has  been  brought  about 

"•  Foochow  was  formerly  the  center  of  the  Chinese  camphor  market.     During  the 
period  of  high  prices  in  1919  about  930,000  Ib.  of  camphor  were  shipped  from  Foochow. 


B1CYCL1C  NON-BENZEN01D  HYDROCARBONS  493 

by  the  manufacture  of  transparent  films  and  sheets  for  automobile 
curtains.  Camphor  was  used  at  one  time  in  the  manufacture  of 
smokeless  powder  and  it  is  still  so  used  to  a  limited  extent  in  some 
sporting  powders.  The  United  States  imports  the  largest  share  of 
the  annual  production  of  natural  camphor  but  with  the  development 
of  the  celluloid  industry  by  the  Japanese,  the  Japanese  Monopoly 
Board  has  seen  fit  to  allot  certain  proportions  of  the  output  to  the 
various  consuming  countries,  a  situation  which  is  having  the  natural 
result  of  stimulating  the  production  of  natural  camphor  in  the  United 
States. 

All  of  the  successful  processes  for  the  manufacture  of  artificial 
camphor  employ  pinene  or  turpentine  as  a  raw  material,  and  while 
the  primeval  camphor  forests  in  Formosa  and  the  interior  of  China 
are  being  rapidly  destroyed,  the  manufacture  of  artificial  camphor  is 
dependent  upon  a  raw  material  the  supply  of  which  is  likewise  rapidly 
diminishing  with  the  destruction  of  the  American  turpentine  forests. 
Turpentine  is  the  largest  item  of  cost  in  the  manufacture  of  artificial 
camphor.  However,  the  use  of  light  petroleum  fractions  and  other 
turpentine  substitutes,  particularly  in  the  paint  and  varnish  industry, 
should  enable  scientific  forestry  to  keep  pace  with  the  consumption  of 
turpentine  in  those  industries  in  which  it  is  indispensable. 

Another  factor  in  the  situation  is  the  planting  of  camphor  trees 
and  the  distillation  of  camphor  from  the  twigs  and  leaves.  (The  cam- 
phor tree  does  not  exude  an  oleoresin  which  can  be  collected  and  sepa- 
rately distilled,  as  in  the  case  of  turpentine.)  The  cultivation  of 
camphor  trees  and  distillation  of  the  leaves  has  been  carried  out  ex- 
perimentally in  numerous  subtropical  localities,  the  Bahamas,117 
Florida,  Ceylon,  Java  and  Formosa,  and  according  to  a  recent  Bul- 
letin of  the  Imperial  Institute  (1920)  the  Japanese  Monopoly  Board 
are  stated  to  have  planted  3,000,000  trees  between  the  years  1900  and 
1906  and  11,000,000  trees  in  the  three  years  following.  In  1913  the 
Board  adopted  the  plan  of  planting  3,000  acres  annually  in  camphor 
trees.  However,  leaf  distillation  has  not  proven  economical  and  the 
total  production  of  Formosan  camphor  has  declined  steadily  since 
1916.  In  1919  the  Japanese  Monopoly  Board  estimated  that  the 
production  of  Formosan  camphor  from  old  trees  would  average  about 
6,500,000  Ib.  annually  and  that  the  trees  set  out  previously,  as  before 
mentioned,  would  be  ready  for  working  about  1930.  In  the  United 

117  Emerson  &  Weidlein,  J.  Ind.  &  Eng.  Chem.  k,  33  (1912)  ;  Eaton,  U.  8.  Devi 
Agric.  Bull.  15  (1912)  ;  Beille  &  Lemaire,  Butt,  de  Pharmaeie  Bordeaux  191Z,  521. 


194       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

States  one  celluloid  company  has  about  3,000  acres  planted  in  cam- 
phor trees  near  Satsuma,  Florida,  and  another  company  is  reported  to 
have  about  12,000  acres  planted  in  camphor  near  Waller,  Florida. 
The  United  States  Department  of  Agriculture  has  a  station  at  Orange 
City,  California,  engaged  in  the  study  of  camphor  cultivation.  The 
cultivation  of  camphor  and  distillation  of  the  leaves  has  also  been 
studied  in  the  Federated  Malay  States  and  at  the  Hakgala  Gardens 
in  Ceylon.  In  the  former  tests  the  yield  of  crude  camphor  varied 
from  1.1  to  2.6  per  cent;  a  yield  of  about  180  pounds  per  acre  per 
year  was  estimated.  Old  wood  of  mature  trees  yields  on  an  average 
about  4  per  cent  of  crude  camphor  oil,  and  air  dry  leaves  of  cultivated 
trees  average  1.5  to  2  per  cent  of  camphor  oil  (75  per  cent  of  which 
is  camphor).  R.  T.  Baker118  has  reported  a  high  yield  of  camphor 
from  the -Australian  species  Cinnamomum  olivieri  and  C.  laubatii. 

Formerly,  crystalline  bornyl  chloride  (usually  miscalled  pinene 
hydrochloride)  was  manufactured  and  sold  under  the  name  of  "arti- 
ficial camphor."  This  product  has  been  known  for  more  than  a  cen- 
tury but  its  usefulness  in  the  manufacture  of  true  camphor  was  not 
appreciated  until  the  development,  since  1906,  of  the  processes  now 
employed  in  the  making  of  synthetic  camphor.  Bornyl  chloride  can- 
not be  substituted  for  camphor  in  the  manufacture  of  celluloid  and 
it  contains  unstable  hydrochlorides,  which  liberate  free  hydrochloric 
acid.  It  is  no  longer  a  common  commercial  article. 

All  known  processes  for  the  industrial  manufacture  of  synthetic 
camphor  involve  the  oxidation  of  borneol  or  isoborneol.  Borneol 
occurs  in  nature  as  "Borneo  camphor"  in  the  wood  of  one  of  the 
Dipterocarpacece  and  in  a  large  number  of  essential  oils,  including 
most  of  the  pine  needle  and  cedar  leaf  oils,  ginger  oil,  et  cetera,  but 
from  none  of  these  natural  sources  can  it  be  produced  cheaply  or  in 
quantity.  The  borneols  are  obtained  industrially  from  bornyl  chlo" 
ride,  and  this  explains  the  use  of  pinene  or  turpentine  as  a  raw 
material.  No  other  material  is  known  from  which  the  borneols  01 
camphor  can  be  manufactured  cheaply  and  in  quantity. 

Turpentines  suitable  for  the  production  of  bornyl  chloride  and 
synthetic  camphor  are  derived  mostly  from  the  long  leaf  pine,  Pinus 
palustris,  of  the  southern  United  States,  the  Cuban  pine,  Pinus  hetero- 
phylla,  and  the  Pinus  pinaster  of  France.  The  turpentines  from  these 
species  consist  almost  exclusively  of  a  and  (3-pinenes.  Small  propor- 
tions of  limonene  and  phellandrene  might  occasionally  be  found  in 

"•Schimmel  &  Co.  Semi-Ann.  Rep.  1911  (1),  38. 


BICYCLIC  NON-BENZENOID  HYDROCARBONS  495 

American  turpentine  since,  as  Herty  and  Dickson119  have  shown 
Pinus  serotina  yields  a  so-called  turpentine  consisting  chiefly  of  limo- 
nene,  but  these  trees  are  scattered  and  relatively  unimportant.  Syl- 
vestrene,  one  of  the  principal  constituents  of  Russian  and  Finnish 
turpentine,  has  never  been  found  in  the  oil  from  American  species. 
The  various  "process  turpentines,"  made  by  solvent  extraction  of  pine 
wood  or  from  stumps,  is  not  suitable  for  the  manufacture  of  bornyl 
chloride  since  such  turpentines  commonly  contain  liberal  proportions 
of  the  solvent  employed  for  its  extraction,  and  other  constituents  which 
have  been  noted  in  such  oils  are  limonene  or  dipentene,  cineol,  terpi- 
neols,  terpinene  and  fenchyl  alcohol.  Turpentine  is  considerably 
modified  by  air  oxidation,  forming  alcohols,  terpineols,  sobrerol, 
formic  and  acetic  acids  and  resinous  substances,  and  since  moisture 
must  be  rigidly  excluded  from  the  preparation  of  bornyl  chloride,  the 
presence  of  very  small  traces  of  alcoholic  or  other  oxidation  products, 
which  can  form  water  by  the  interaction  of  hydrogen  chloride,  very 
materially  decreases  the  yield  of  bornyl  chloride  and  the  use  of  old 
turpentine  which  has  been  exposed  to  air  oxidation  should  accordingly 
be  avoided. 

Testing  of  Turpentine: 

(a)  Specific  Gravity:    This  should  be  within  the  limits  0.862  to 
0.870  at  20°C.    Lower  specific  gravity  would  indicate  the  presence 
of  petroleum  naphtha.    A  higher  specific  gravity  would  indicate  the 
presence  of  wood  turpentine,  "pine  oil"  (terpineols),  or  that  the  tur- 
pentine has  become  oxidized  by  long  storage. 

(b)  Boiling-point:    Nothing  should  distill  below  154°C.  (except  a 
drop  or  two  of  water),  and  75%  should  distill  below  160°.    Some 
specifications  require  that  95%  should  distill  below  170°.    Petroleum 
naphthas  are  sometimes  very  closely  cut  so  as  to  boil  within  this  range 
(154°  to  170°),  but  ordinarily  will  show  some  distillate  below  154°. 
Limonene  and  dipentene  boil  at  176°  and  any  considerable  amount 
will  be  thus  indicated.    The  terpineols  boil  at  210°-218°.    Rosin 
spirit  has  a  wide  range  of  boiling-point,  like  petroleum  naphtha,  and 
also  contains  considerable  dipentene. 

(c)  Optical  Rotation:     It  is  not  known  whether  pinenss  of  low 
optical  rotation  give  better  yields  of  bornyl  chloride,  as  is  the  case 
with  crystalline  nitrosyl  chlorides,  or  not. 

"•  J.  Am.  Chen*.  8oc.  SO,  872  (1908). 


496 


CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


(d)  Refractive  Index:    At  20°C.  this  should  be  within  the  limits 
1.4680  to  1.4760.    Low  values  would  indicate  petroleum  naphtha. 

(e)  Bromine  and  Iodine  Numbers:     These  are  chiefly  useful  in 
detecting  petroleum  naphtha  but  are  hardly  necessary  when  the  other 
tests  are  made.     It  is  difficult  to  carry  out  these  determinations  and 
get  accurate,  concordant  results  as  with  fatty  oils,  owing  to  substitu- 
tion reactions  taking  place  with  formation  of  halogen  acid. 

Effect  of  Other  Constituents  on  Bornyl  Chloride  Preparation: 

(1)  (3-pinene  yields  the  same  hydrochloride  as  a-pinene: 

(2)  Camphene,  a  minor  constituent  of  turpentine  oil,  yields  a  low 
melting,   unstable    hydrochloride   which   probably    yields    camphene 
readily  in  the  autoclave  process.     Its  presence  is  not  objectionable 
but  is  partly  responsible  for  the  partial  decomposition  of  the  crude 
bornyl  chloride,  free  HC1  being  given  off. 

(3)  Water:     The  presence  of  moisture  in  the  reaction  mixture 
causes  the  pinene  to  be  converted  chiefly  into  dipentene  dihydro- 
chloride. 


which  melts,  when  pure,  at  50°,  but  the  impure  mixture  remains  oily 
and  retains  considerable  bornyl  chloride  in  solution.  Dipentene  dihy- 
drochloride  is  much  less  stable  than  bornyl  chloride  and  when  such 
an  oily  mixture  is  heated,  it  is  readily  decomposed  to  free  HC1  and 
dipentene. 

... .;  (4)  Limonene,  the  optically  active  form  of  dipentene,  forms  the 
dihydrochloride  and  diminishes  the  yield  of  bornyl  chloride  in  the 
manner  indicated  above. 

(5)  Terpineols  and  other  Alcohols  yield  water  when  treated  with 
HC1;  cf.  item  (3). 


B1CYCL1C  NON-BENZENOID  HYDROCARBONS  497 

(6)  Organic  acids  also  cause  the  reaction  with  hydrogen  chloride 
to  go  too  far,  with  rupture  of  the  C5  ring  to  form  dipentene  dihydro- 
chloride. 

Distillation  and  Drying  of  the  Turpentine:  The  secret  of  obtain- 
ing good  yields  of  bornyl  chloride  is  effective  drying  and  purification 
of  the  turpentine.  Mere  drying  is  not  sufficient  as  it  is  necessary  to 
remove  or  destroy  alcohols  or  other  substances  which  yield  water  when 
treated  with  HC1,  and  metallic  sodium  is  therefore  best  for  this  dual 
purpose.  The  still,  which  may  be  of  iron  or  copper,  should  be  pro- 
vided with  a  stirrer  so  that  after  the  sodium  is  melted  it  will  be  thor- 
oughly emulsified  in  the  oil.  A  small  fractionating  column  is  advis- 
able, in  which  case  90  per  cent  of  American  turpentine  can  be  used  for 
the  preparation  of  bornyl  chloride. 

Turpentine  and  Hydrogen  Chloride:  When  the  pinene  has  been 
well  dried  and  purified  from  oxidation  products  and  the  hydrogen 
chloride  is  carefully  dried,  preferably  by  sulfuric  acid  Sp.  Gr.  1.84, 
a  yield  of  bornyl  chloride  corresponding  to  about  75  per  cent  of  the 
theory  can  be  obtained.  Lead-lined  or  glass-enameled  mixing  vessels 
should  be  employed;  iron,  or  alloys  or  other  material  which  can  yield 
iron  chloride  give  liquid  chlorides.  Reaction  temperatures  above  30° 
yield  increasing  proportions  of  liquid  chlorides  but  the  reaction  with 
hydrogen>chloride  is  slow  below  — 15°.  Dry  neutral  solvents  such  as 
petroleum  ether  or  carbon  tetrachloride  can  be  employed  without 
diminishing  the  yield  of  bornyl  chloride  and  the  solidification  of  the 
reaction  mixture  can  thus  be  prevented,  but  alcohol,  ether  or  glacial 
acetic  acid  cause  liquid  chlorides  to  be  formed. 

Bornyl  chloride  is  remarkably  stable  for  a  chlorine  derivative  of 
the  non-benzenoid  hydrocarbon  series.  The  statements  in  the  earlier 
literature  that  it  is  decomposed  slowly  at  room  temperature  and  fairly 
rapidly  at  100°  probably  refers  to  the  decomposition  of  the  crude 
product  containing  unstable  impurities  such  as  dipentene  dihydro- 
chloride  and  camphene  hydrochloride.  Wallach  12°  states  that  bornyl 
chloride  distills  practically  without  decomposition  at  207°-208°,  a 
fact  which  is  familiar  to  those  experienced  in  this  field.  Bornyl  chlo- 
ride, once  formed,  is  not  changed  by  further  treatment  with  hydrogen 
chloride,  either  dry  or  in  the  presence  of  moisture.  True  pinene  hy- 
drochloride is  readily  converted  to  dipentene  dihydrochloride  by  HC1. 
Pinene  hydrochloride  has  never  been  isolated  from  the  products  of 

110  Ann,  £39,  4   (1887). 


498       CHEMISTRY  OF  THE  NON-BENZEN01D  HYDROCARBONS 

the  reaction  of  pinene  and  hydrogen  chloride  but  was  made  by  Wal- 
lach121  from  nopinone  by  means  of  magnesium-methyl  iodide. 


0 


CH3-C-CH3 

xlx 

nopinone 


tCH3MQI 


Ci 


pinene  hydro  chloride 


The  mixture  of  oily  chlorides  accompanying  the  crude  bornyl  chlo- 
ride contains  nearly  50  per  cent  of  bornyl  chloride  in  solution;  thus, 
equal  quantities  of  bornyl  chloride  melting  at  131°  and  dipentene 
dihydrochloride  melting  at  50°,  melt  down  to  an  oil  at  room  tempera- 
ture 20°  to  22°,  and  fenchyl  chloride,  which  is  an  oil,  has  a  similar 
solvent  effect.  When  the  oily  chloride  mixture  is  heated  to  about 
180°,  the  unstable  chlorides  are  decomposed  and  a  fairly  brisk  libera- 
tion of  hydrogen  chloride  results.  The  resulting  terpenes,  chiefly 
dipentene,  may  then  be  distilled  and  the  subsequent  fractions  boiling 
from  185.°-215°  yield  an'  additional  quantity  of  crystalline  bornyl 
chloride.  About  10  per  cent  of  the  original  oily  chloride  mixture 
remains  behind  as  a  heavy  viscous  mixture  of  polymers?.  The  amount 
of  crystalline  bornyl  chloride  which  is  recoverable  in  this  way  is 
equivalent  to  about  35  to  38  per  cent  of  the  original  oily  chlorides, 
when  these  chlorides  are  separated  originally  at  — 15°. 

The  formation  of  bornyl  chloride  from  pinene  and  hydrogen  chlo- 
ride is  exothermic.122 

On  account  of  the  extraordinary  stability  of  bornyl  chloride  many 
attempts  have  been  made  to  employ  catalysts  to  facilitate  either  the 
formation  of  camphene  or  conversion  to  bornyl  esters.  Anhydrous 
aluminum  chloride  reacts  energetically  with  bornyl  chloride,  evolving 
hydrogen  chloride  and  causing  further  decomposition  and  polymeriza- 
tion. Anhydrous  ferric  chloride  is  markedly  less  active  and  fused 
zinc  chloride  is  still  less  active.  Stannic  chloride  and  titanium  chlo- 
ride are  much  like  zinc  chloride  in  their  effect  on  bornyl  chloride. 
Cuprous  chloride,  or  finely  divided  copper,  is  claimed  to  have  a  cata- 

121  Ann.  356,  227  (1907). 

1MGuiselin,  Chem.  Ztg.  SI,  1299  (1910).     Large  scale  work  ihowed  119,000  calorie* 

liberated  on  treating  100  kilos  of  turpentine. 


are 


BICYCLIC  NON-BENZEN01D  HYDROCARBONS  499 

lytic  effect  upon  a  wide  variety  of  reactions  of  both  alkyl  and  aryl 
chlorides,  as  in  the  manufacture  of  glycol,123  or  the  conversion  of 
chlorobenzene  to  phenol,12*  but  appears  to  be  of  no  value  in  reactions 
of  bornyl  chloride.  Barium  chloride  markedly  catalyzes  the  decom- 
position of  simple  alkyl  chlorides  to  olefines 125  and  calcium  chloride 
causes  rapid  condensation  of  benzyl  chloride.  But  zinc  chloride  ap- 
pears to  be  the  only  catalyst  appearing  in  the  patent  literature  of  the 
bornyl  chloride  reactions.126  The  purpose  of  this  catalyst  is  to  avoid 
the  higher  temperatures  and  pressures  usually  necessary  for  the  com- 
plete conversion  of  bornyl  chloride  to  camphene  and  bornyl  acetate, 
when  acetic  acid  and  sodium  acetate  are  used.  However,  considerable 
polymerization  invariably  takes  place  and  one  patentee 127  seeks  to 
avoid  this  by  introducing  sodium  acetate  at  intervals  which  has  the 
effect  of  converting  the  zinc  chloride  into  zinc  acetate  and  sodium 
chloride,  the  latter  separating  on  account  of  its  slight  solubility  in 
acetic  acid.  Another  patentee  refluxes  a  solution  of  bornyl  chloride 
in  formic  or  acetic  acids  and  adds  zinc  formate  or  acetate.128  These 
reactions  are  quite  analogous  to  the  conversion  of  chloropentanes  to 
amyl  acetates  by  heating  with  sodium  acetate  in  acetic  acid  solutions. 
In  both  cases  zinc  salts  cause  the  formation  of  10  to  25  per  cent  of 
heavy  viscous  polymerized  hydrocarbons. 

Conversion  of  Bornyl  Chloride  to  Camphene  and  Bornyl  Acetate. 

In  the  following  discussion  no  attempt  is  made  to  distinguish  be- 
tween camphene  and  bornylene. 

The  difficulty  with  most  of  the  processes  for  making  camphene 
from  bornyl  chloride  by  heating  with  alkalies,  is  chiefly  a  mechanical 
one,  i.  e.,  the  insolubility  of  bornyl  chloride  in  alkalies  and  inorganic 
alkaline  mixtures.  Naturally  vigorous  agitation  affords  better  con- 
tact of  the  reacting  substances  and  the  presence  of  a  fine  solid  sus- 
pension, milk  of  lime,  assists  in  the  emulsification.129  The  addition 
of  fatty  acid  soaps  has  been  proposed130  and  molten  alkali  pheno- 
lates131  also  have  been  suggested.  Complete  miscibility  is  obtained 

"•Matter,  U.   S.  Pat.  1,237,076. 

124  Meyer  &  Bergius,  U.  S.  Pat.  1,062,351;  Ber.  47,  3155   (1914) 

12*Braun  &  Deutsch,  Ber.  45,  1271    (1912). 

126  Bergs,   U.   S.  Pat.   903,047;   Weizman,   U.   S.   Pat.   910,978;   von   Hcyden,   U.    S. 
Pat.  919,762. 

127  Ruder,  U.  S.  Pat.  1,105,378. 
128Philipp,  U.  S.  Pat.  919,762. 

128  Schmitz  &  Stalman,  U.  S.  Pat.  1,030,334. 
18°Stephan,  U.  S.  Pat.  725,890. 

111  Koch,  U.  S.  Pat.  970,829  ;  Bergs,  U.  S.  Pat.  833,666. 


500      CHEMISTRY  OF  THE  NON-BtfNZENOID  HYDROCARBONS 

when  bornyl  chloride  is  heated  with  organic  bases  such  as  aniline,132 
naphthylamine,133  pyridine,134  or  alcoholic  ammonia.135  The  aniline 
process  gives  very  good  yields,  about  90  per  cent  of  the  theory  but  an 
excess  of  aniline  is  necessary,  as  otherwise,  bornyl  aniline  hydrochlo- 
ride  is  formed  and  this  substance  is  not  easily  decomposed. 

When  bornyl  chloride  is  heated  with  sodium  acetate  in  acetic  acid 
in  an  autoclave  to  180°  to  200°  the  bornyl  chloride  is  almost  quan- 
titatively converted  into  camphene 138  and  bornyl  acetate.  The  cam- 
phene  and  acetic  acid  may  be  distilled  together  from  the  resulting 
reaction  mixture  and  converted  to  bornyl  acetate  by  the  addition  of  a 
small  quantity  of  sulfuric  acid  according  to  the  well-known  method  of 
Bertram  and  Wahlbaum.  (In  order  to  separate  the  bornyl  acetate 
thus  formed  from  the  excess  acetic  acid  without  diluting  with  water, 
a  slight  excess  of  sodium  acetate  may  be  added  to  form  sodium  sulfate 
and  acetic  acid,  followed  by  fractional  distillation  in  vacua.) 

Bertram  and  Wahlbaum137  originally  recommended  acetylating 
camphene  at  50°,  using  a  mixture  such  as  the  following:  2000  cc. 
acetic  acid,  1000  cc.  camphene,  50  cc.  water  and  50  g.  sulfuric  acid. 
Verley  138  recommends  much  more  water,  as  indicated  by  the  follow- 
ing: 450  parts  sulfuric  acid  diluted  to  60  to  66  per  cent,  100  parts 
camphene,  100  parts  acetic  acid,  the  mixture  being  vigorously  agitated 
at  30°.  Still  better  results,  according  to  the  writer's  experience,  are 
obtained  by  the  method  of  Behal,139  according  to  which  the  Bertram- 
Wahlbaum  mixture  is  allowed  to  stand  at  room  temperature  for  24 
hours.  The  formation  of  polymers  is  much  reduced  by  operating  at 
the  lower  temperatures.  With  pure  camphene  the  yield  of  bornyl 
acetate  is  92  to  94  per  cent  of  the  theory.  When  the  resulting  bornyl 
acetate  is  fractioned  in  vacuo,  unchanged  hydrocarbons  pass  over  with 
the  acetic  acid  fractions.  Several  other  modifications  of  the  Bertram- 
Wahlbaum  reaction  are  obviously  mere  patent  word  play. 

It  is  possible  that  sodium  formate  and  formic  acid  can  be  sub- 
stituted for  acetic  acid  and  acetate;  in  fact,  such  a  process  is  described 
by  Dubosc.140  Henry  has  shown  that  sodium  formate  in  methyl 
alcohol,  and  an  alkyl  halide,  gives  excellent  yields  of  the  corresponding 

182  German  Pat.  205,850   (1907)  ;  Bruhl,  Ber.  25.  146   (1892)  ;  Ullmann  &  Schrnid, 
Ber.  43,  3202   (1910). 

183  German   Pat.   206,386    (1907). 
13*Weizmann,  U.  S.  Pat.  896,962. 
""German  Pat.  264,246   (1912). 
188Wallach,  Ann.  252,  6. 

187  J.  prakt.  Chem.   (2)   $9,  1   (1894)  ;  German  Pat.  67,255. 

188  U.   S.  Pat.  907,428    (1908). 
"•Austrian  Pat.  38,203   (1908). 
140  Brit.  Pat.  14,379   (1907). 


BICYCLIC  NON-BENZENOID  HYDROCARBONS  501 

alcohol,141  and  ethylene  chloride  can  be  smoothly  converted  to  the 
glycol  by  this  reaction.142  Bornyl  chloride  is  so  remarkably  stable, 
however,  that,  when  using  methanol,  the  reaction  is  slow  at  180°  and 
330  Ibs.  pressure.  Heating  bornyl  chloride  with  alkali  oxalates  has 
also  been  tried.143 

Other  Processes  for  Manufacturing  Borneol  or  Bornyl  Esters. 

The  first  attempt  to  manufacture  artificial  camphor  on  an  indus- 
trial scale  was  in  1900  at  Niagara  Falls,  where  the  Thurlow  process14* 
was  operated  by  the  Ampere  Electrochemical  Co.  At  that  time,  tur- 
pentine could  be  had  for  about  35  cents  per  gallon  but  the  yields  of 
borneol  were  so  low  that  the  cost  of  artificial  camphor  by  this  method 
was  considerably  greater  than  the  market  price  of  natural  camphor 
and  the  process  was  accordingly  soon  abandoned.  In  the  Thurlow 
process  anhydrous  oxalic  acid  was  added  to  dry  turpentine  at  120°- 
130°.  The  reaction  is  energetic  and  much  material  was  lost  by  the 
reaction  becoming  too  violent.  Dipentene  was  separated  from  borneol 
esters  by  distilling  with  steam,  the  esters  saponified  and  the  borneol 
oxidized  to  camphor  by  chromic  acid  mixture.  It  was  found  most 
expedient  to  purify  the  borneol  before  oxidation  rather  than  to  purify 
the  camphor  made  from  impure  borneol. 

The  Thurlow  process  had  quite  a  few  European  modifications. 
Zeitschel145  heated  pinene  and  glacial  acetic  acid  to  200°  for  five 
hours  and  reported  a  yield  of  10  to  15  per  cent  camphene,  about  40 
per  cent  bornyl  acetate  and  the  remainder  was  dipentene.  According 
to  the  writer's  experience  the  yields  of  camphene  and  bornyl  acetate 
are  not  improved  by  the  addition  of  acetic  anhydride.  Fenchyl  alco- 
hol is  also  formed  and  Bouchardat  and  Lafont  observed 146  the  forma- 
tion df  fenchyl  alcohol  when  using  benzoic  acid  under  similar  condi- 
tions. Bischler  and  Baselli 147  treated  camphene  with  anhydrous 
oxalic  acid  at  110°-115°;  Seifert148  used  salicyclic  acid  and  pinene  at 
110°  for  50  hours;  Austerweil 149  used  "poly-substituted  acids";  Hert- 
korn150  heated  turpentine  with  boric  acid  and  absolute  alcohol,  etc. 

141  Bull.  acad.  roy.  Belg.  1902,  445. 

142  Brooks   and    Humphrey,   U.    S.   Pat.    1,215,903;    J.   Ind.    d   Eng.    Chem.   9t   750 

143  Charles,  Eng.  Pat.  5.549   (1904). 

144  U.  S.  Pat.  698,761 ;  833,095. 

146  U.  S.  Pat.  907,941. 
1MCompt.  rend.  113,  551. 

147  U.  S.  Pat.  876,310. 

148  U.  S.  Pat.  779,377. 

149  U.  S.  Pat.  986,038. 
"°U.  S.  Pat.  901,293. 


502       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

It  is  claimed  151  that  by  the  action  of  tetrachlorophthalic  acid  on 
turpentine  at  106°-108°  (12  hours)  and  finally  at  140°  (six  hours) 
that  esters  of  borneol  are  formed  and  that  the  borneol  thus  obtained, 
after  saponification  of  the  ester,  is  quite  free  from  isoborneol.  This 
method  should  therefore  be  operated  to  advantage  in  conjunction  with 
the  method  of  catalytically  oxidizing  the  borneol  to  camphor  by  pass- 
ing over  heated  copper,  since  isoborneol  is  chiefly  decomposed  to 
camphene  by  this  treatment. 

Hesse152  has  described  the  reaction  of  bornyl  chloride,  with  mag- 
nesium in  ether,  as  in  the  well-known  Grignard  reaction,  and  oxidizing 
the  magnesium-bornyl  chloride  by  air  or  oxygen  to  obtain  borneol. 
This  reaction,  although  patented,  is  of  little  interest  since,  like  all  the 
more  complex  alkyl  halides,  the  reaction  with  magnesium  is  very  slow 
and  the  main  reaction  is  one  of  condensation, 

(a)  C10H17C1  +  Mg  -     ->  C10H17MgCl 

(b)  C10H17MgCl  +  C10H17C1  -     -»  MgCl2  +  C20HM 

Regardless  of  its  high  cost,  this  method  is  not  even  a  good  laboratory 
method. 

By  reacting  upon  bornyl  chloride  with  milk  of  lime  vigorously 
stirred,  at  a  comparatively  low  temperature,  135°  to  150°  for  about 
three  days,  an  alcohol  isomeric  with  borneol  is  obtained.153  This  alco- 
hol, camphene  hydrate,  is  much  less  stable  than  borneol,  melts  at 
149°-150°,  boils  at  206°  and  on  heating  with  dilute  acids  is  readily 
converted  to  camphene.  This  instability  would  indicate  the  struc- 
ture of  a  tertiary  alcohol  but  its  constitution  is  not  yet  definitely 
known. 

The  treatment  of  pinene  with  ozone  has  also  been  described  in  a 
patented  process  154  but  hydrolysis  of  pinene  ozonide  does  not  really 
give  borneol  or  camphor  but  pinonic  acids  (q.v.)  and  a  series  of  other 
products.  Bornylene  ozonide  might  be  expected  to  give  camphor  on 
hydrolysis.  The  oxidation  of  borneols  to  camphor  by  ozone  has  also 
been  patented155  but  the  industrial  value  of  all  oxidation  methods 
depending  upon  ozone  is  questionable. 


Pat  *       aqUeS  de  produits  chimi(lues  de  Tfaan  et  de  Mulhouse. 

' 


168  Sobering,  'German  Pat.  219,243    (1908);  Ber.  41,  1092    (1908). 

1MKnox,  U.  S.  Pat.   1,086,372    (1914). 

1MStephan  &  Hunsalz,  U.   S.  Pat  801,483   (1905). 


BICYCLIC  NON-BENZENOID  HYDROCARBONS  503 

Borneol  and  Isoborneol 

The  relation  of  camphor  to  borneol  is  shown  by  the  formation  of 
borneol  from  camphor  by  reduction  by  sodium  and  alcohol. 
CH3  CH3 

I                                                          I  H 

CH2 C C  =  0  CH2-       -C C< 


CH. 


—  C  — CH3 


OH 


CH2 C CH5 

H 

In  addition  to  borneol,  the  closely  related  isoborneol  is  also  formed 
in  this  reaction.  The  two  borneols  are  commonly  believed  to  be 
stereoisomers,  i.  e., 

CH3  CH3 

H  OH 

CH2 C C< 

OH 
CH3  —  C  —  CH, 

CH2 C CH2 

H 

Both  yield  camphor  on  oxidation  and  their  behaviors  on  oxidation  are 
nearly  identical  and  for  the  purpose  of  manufacturing  synthetic  cam- 
phor need  not  be  separately  considered.  Isoborneol  is  the  principal 
product  of  the  hydration  of  camphene  in  the  Bertram-Walbaum  reac- 
tion. Isoborneol  is  somewhat  less  stable  than  borneol  and  yields  a 
"camphene,"  melting-point  50°,  when  decomposed  by  the  action  of 
zinc  chloride  or  dilute  sulfuric  acid. 

Isoborneol  Borneol 

Crystal  form  hexagonal  hexagonal 

Melting-point    212°  203°-204° 

Solubility  in  benzene  at  0° 1:2%  1:6% 

Solubility  in  ligroin  at  20° 1 :2%  1 :6 

Phenylurethane,  M.-P 138°-139°  138°-139° 

Chloral  compound,  M.-P liquid  55°-  56° 

Bromal  compound,  M.-P : .      72°  98°-  99° 

Zinc  chloride,  conversion  to f  camphene  unchanged 

Dil.  sulfuric  acid,  conversion  to \  M.-P.  50°  unchanged 

Sulfuric  acid  +  CHaOH    CIL  ether  unchanged 

Oxidation  by  CrOa  camphor  camphor 

Oxime  of  camphor  produced,  M.-P 118°  118° 

Para-nitrobenzoate  "•    129°  137° 

156  Henderson  &  Heilbron,  Proc.  Chem.  Soc.  t9,  381  (1913).  The  nitrobenzoate  is 
conveniently  prepared  by  treating  with  p-nitrobenzoyl  chloride  in  pyridine. 


504       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

When  borneol  or  isoborneol  is  decomposed  with  loss  of  water,  two 
hydrocarbons  are  produced,  camphene  being  the  principal  product. 
The  hydrocarbon  formed*  in  smaller  proportions  is  bornylene  and  this 
hydrocarbon  retains  the  structure  of  the  parent  alcohols. 


CH 


CH 


A  great  deal  of  work  has  been  done  upon  the  structure  of  camphene 
and  bornylene,  which  is  reviewed  elsewhere  (q.v.)  but  in  the  earlier 
literature  no  distinction  is  made  between  these  two  hydrocarbons. 
Tschugaeff's  method  of  preparing  olefines  by  decomposing  the  methyl 
xanthate  esters  gives  a  fairly  pure  bornylene  when  applied  to  the 
decomposition  of  borneol.157  Tschugaeff's  bornylene  melted  at  109° 
to  109.5°  and  boiled  at  146.5°.  Dezfro-bornylmethyl  xanthate  yields 
Zce?;o-bornylene  and  vice  versa,  an  interesting  example  of  the  Walden 
inversion.  Bornylene  is  noteworthy  for  its  high  melting-point,  as 
compared  with  all  other  hydrocarbons,  i.  e.,  113°,  and  its  boiling-point 
146°.  Bornylene  is  less  readily  acetylated  than  camphene,  by  the 
Bertram-Walbaum  method.  A  less  pure  bornylene  may  be  made  by 
treating  bornyl  iodide  with  alcoholic  caustic  potash.  Bornylene  is 
also  more  resistant  to  oxidation  than  camphene  and  Henderson  and 
Caw 15S  accordingly  purified  bornylene  by  oxidation  by  hydrogen 
peroxide  and  obtained  a  specimen  showing  the  melting-point  113°  and 
boiled  at  146°.  A  very  pure  bornylene  made  through  camphocarbonic 
acid159  also  showed  a  melting-point  of  113°,  and  a  boiling-point  of 
146°. 

CH.C02H  CH.C02H.  C.C02H  CH 

C8H14<  |  •*  C8H14<  7         -+  C8H14<  ||          ->  C8H14<  || 

c  =  o  CHOH  CH  CH 

It  is  still  generally  believed  that  "camphene"  may  be  a  mixture  of 
hydrocarbons,  or  that  camphenes  of  different  origin  are  not  identical. 
The  camphenes  from  various  natural  sources  differ  widely  in  physical 

167  Ann.  388,  260   (1912). 

188  J.  Chem.  Soc.  101,  1416   (1912). 

"•Bredt,  Ann.  366,  11   (1909)  ;  ,7.  prakt.  CJiem.   (2)   81,,  778   (1911). 


NON-BENZENOID  HYDROCARBONS  505 

properties.    Wallach160   isolated   a   specimen   of   camphene   from   a 
Siberian  pine-needle  oil  which  showed  a  low  melting-point,  39°,  a  boil- 

4ft  ° 
ing-point  of  160°-161°,  d4QO  0.8555,  [a]D  — 84.9°  and  n_1.46207. 

Camphene  made  from  bornylamine  161  melts  at  50°  and  showed  the 
high  rotation  of  [<*]T\    103.89°.    Ordinary  camphene  hydrochloride, 

melting  at  155°,  is  identical  with  the  chloride  of  isoborneol. 

Oxidation  of  Borneol  and  Isoborneol 

As  stated  above,  the  old  Thurlow  process,  practiced  at  Niagara 
Falls  about  1900,  employed  chromic  acid  for  oxidation  of  the  borneols 
to  camphor.  Various  special  modifications  of  the  chromic  acid  oxida- 
tion method  have  been  described  in  the  patent  literature,  and  the 
processes  of  Verley,162  Florizoone,163  Jluder 16*  and  Weizmann 165  men- 
tion the  use  of  a  solvent  added  to  insure  thorough  exposure  of  the 
borneol  to  the  oxidizing  solution.  Carbon  tetrachloride,  benzene  and 
acetone 165  are  useful  for  this  purpose,  but  acetic  acid  forms  appre- 
ciable proportions  of  bornyl  acetate  which  resist  oxidation  to  cam- 
phor. Verley  recommends  50  parts  of  sodium  dichromate,  68  parts 
of  sulfuric  acid  and  600  parts  of  water  but  Ruder  employs  solutions 
of  about  one  third  this  concentration.  Free  sulfuric  acid  should  be 
avoided  as  much  as  possible  on  account  of  the  decomposition  of  iso- 
borneol to  camphene,  which  is  more  resistant  to  oxidation,  by  heating 
with  dilute  sulfuric  acid,  as  noted  above.  Gradually  acidifying  the 
reaction  mixture  as  the  oxidation  proceeds  is  therefore  advantageous. 
The  oxidation  of  camphene  itself  by  chromic  acid  has  been  de- 
scribed 166  but  the  yields  are  lower  than  when  borneols  are  employed. 
Another  patentee 167  proposed  to  employ  potassium  persulfate  for  the 
oxidation  of  camphene.  The  use  of  sodium  dichromate  or  chromic 
acid  for  this  purpose,  on  a  tonnage  scale,  involves  the  electrolytic 
regeneration*68  of  this  oxidizing  material  or  its  utilization  as  basic 
chromium  salt  solutions  in  tanning  or  the  mordanting  of  textile 
goods,  otherwise  the  method  would  be  too  costly. 

"Ann.  S57f  79   (1907). 
"Wallach,  Ann.  357,  84   (1907). 
82  U.   S.   Pat.   908,171    (1908). 
88  Brit.   Pat.  5,513    (1908). 
MU.  S.  Pat.  1,066,758    (1913). 
"Brit.  Pat.  21,946   (1907). 

"Dubosc,  Brit.  Pat.  8260-A   (1906)  ;  8356-A  (1906). 
67  Sauvage,   French   Pat.   389,092. 

MGes.  Chem.  Ind.  Basel, — French  Pat.  387,539;  LeBlanc,  Z.  Elektrochem.  7.  290 
(1900)  ;  McKee  &  Leo,  J.  Ind.  &  Eng.  Chem.  12f  16   (1920). 


506      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

The  yields  of  camphor  by  oxidizing  the  borneols  by  air,  in  the 
absence  of  catalysts,  are  very  poor,169  but  catalytic  dehydrogenation 
of  borneol  to  camphor,  by  jneans  of  finely  divided  copper170  at  175°- 
180°  or  reduced  nickel 171  at  200°-240°  is  said  to  have  been  practiced 
industrially.  Aloy  and  Brustier 172  state  that  when  borneol  is  passed 
over  copper  at  300°  the  yield  of  camphor  is  quantitative  but  that 
above  320°  the  yield  of  camphor  is  progressively  diminished  until  at 
420°  hydrocarbons  only  are  produced.  Camphor  is  not  reduced  to 
borneol  by  hydrogen  and  catalytic  nickel  at  180°-200°,  either  alone 
or  in  solution  in  cyclohexanol.  Neave  173  states  that  borneol  yields 
camphor  in  nearly  quantitative  yields  by  passing  over  finely  divided 
copper  at  300°  but  that  isoborneol  under  the  same  conditions  gives 
chiefly  camphene.  Thorium  oxide  at  350°  yields  a  terpene  mixture 
boiling  at  150°  to  180°,  the  constituents  of  which  were  not  definitely 
characterized.17*  Small  proportions  of  unchanged  bornyl  chloride  or 
other  chlorides  poison  the  catalyst  unless  the  material  is  previously 
purified  to  remove  such  chlorides,  as,  for  example,  by  digesting  with 
a  little  inert  solvent  over  metallic  sodium. 

Quite  a  number  of  processes  for  the  oxidation  of  the  borneols  by 
nitric  acid  or  oxides  of  nitrogen  have  been  described.  Hesse 175  used 
pure  concentrated  nitric  acid;  another  process176  prescribes  nitric  acid 
containing  oxides  of  nitrogen,  at  10°  to  15°,  and  nitrous  acid  itself  is 
said  to  give  excellent  yields.177  The  addition  of  small  amounts  of 
vanadium  pentoxide  to  the  nitric  acid  is  claimed  to  be  advantageous 
and  several  patents  have  recently  been  granted  to  Andreau,178  who 
employs  a  mixture  of  about  339  parts  of  sulfuric  acid  66°  Be,  and 
253  parts  of  nitric  acid,  26°  Be,  and  who  notes  that  once  the  oxidation 
has  been  initiated  by  raising  the  temperature  to  about  40°,  the  reac- 
tion may  then  be  carried  out  smoothly  with  cooling  so  that  the  tem- 
perature does  not  rise  above  40°.  In  the  nitric  acid  process  the  cam- 
phor forms  a  liquid  double  compound  with  the  nitric  acid,  which 
floats  on  the  acid  mixture  as  a  sparingly  soluble  oil 'layer.  This 
obviates  the  use  of  a  solvent  to  insure  complete  oxidation  of  the 

1MCf.  Stephan  &  Rehlander,  TL   S.  Pat.  801,485. 

170  Sobering,   German   Pat.   161,523;  Goldsmith,   Brit.   Pat.   17,573    (1906). 
171Aschan   &   Kempe,    U.    S.   Pat.   994,437    (1911)  ;    Zimmerman,    Brit.    Pat.    26,708 
(1904) .  .  i 

172  Bull.  soc.   chim.    (4)    9,  733    (1911). 
178  J.  Chem.  Soc.  101,  513   (1912). 

174  Aloy  &  Brustier,  J.  pharm.  chim.   (7)   10,  49   (1914). 
™Ber.  39,  1144,  (1906). 

Ges-   Chem-   Ind-   Basel,   Brit.   Pat.   9,857    (1907);   Philip,   Austrian   Pat.   33,720 

. 

177  Boehringer  &  Son,  U.  S.  Pat.  802,793   (1904). 

178  U.  S.  Pat.  1,347,071   (1920). 


BICYCLIC  NON-BENZENOID  HYDROCARBONS  507 

borneol,  enclosure  of  borneol  particles  by  solid  camphor  being  avoided. 
The  oily  nitric  acid  compound  is  decomposed  by  water,  precipitating 
the  camphor.  Camphoric  acid  and  nitrocompounds  are  also  formed, 
the  latter  coloring  the  crude  camphor  light  yellow,  and  imparting  to 
it  a  peculiar  "nitro"  odor. 

Practically  every  known  method  of  oxidizing  organic  compounds 
has  been  proposed  for  the  oxidation  of  the  borneols,  or  camphene,  to 
camphor,  including  chlorine,179  hypochlorites,180  potassium  perman- 
ganate both  in  acid 181  and  alkaline 182  solution,  etc.  When  perman- 
ganate is  employed  the  camphor  formed  is  removed  from  the  spent 
mixtures  by  distilling  with  steam.  Camphene,  in  dilute  acetone,  has 
also  been  oxidized  by  potassium  permanganate,  to  camphor.183  All  of 
these  methods  using  permanganate  are  relatively  very  costly,  except 
where  methods  for  its  regeneration  have  been  perfected. 

Impurities  of  Crude  Synthetic  Camphor 

If  the  borneol  or  isoborneol  is  not  purified  before  oxidation,  the 
resulting  camphor  will  contain  small  proportions  of  the  fenchones, 
which,  like  camphor,  are  quite  resistant  to  further  oxidation  and  form 
very  stable  double  compounds  with  nitric  acid. 

The  behavior  of  the  fenchenes  in  the  Bertram- Walbaum  reaction 
follows  the  general  esterification  behavior  of  unsaturated  terpenes. 
Komppa  and  Hinticka 184  share  Quist  's  view  that  isof enchene,  boiling- 
point  152°-155°  has  the  constitution. 

CH3 
CH  — CH— C< 

CH. 

H, 


CH— c — CH, 

CH3 


As  noted  above  the  chief  impurity  in  bornyl  chloride  is  dipentene 
dihydrochloride  but  fenchyl  chloride  is  present  in  the  oily  part  of  the 

178  Boehringer  &  Son,  TJ.  S.  Pat.  802,792;  Brit.  Pat.  28,035    (1904). 
180Hertkorn,  U.  S.  Pat.  901,708  (proposes  the  addition  of  salts  such  as  CuCla  and 
FeCl3)  ;  Glaser,  U.  S.  Pat.  875,062;  864,162   (1907). 

181  Semmler,  Ber.  33,  3430  (1900). 

182  Sobering,  German  Pat.  157,590  (1903)  ;  Stephan  and  Hunsalz,  U.  S.  Pat.  770,940 
(1904) . 

188Behal,  Austrian   Pat.   38,203    (1908). 
1MChem.  Abs.  13,  2864   (1919). 


508      CHEMISTRY  OF  THE  NON-BENZEN01D  HYDROCARBONS 


hydrochloride  mixture  since  fenchene  has  been  found  in  the  crude 
camphene  made  from  these  chlorides.  Aschan  185  represents  the  for- 
mation of  bornyl  chloride  and  fenchyl  chloride  as  follows, 

CH3 


CH-( 

:-CH 

3 

bornyl  chloride 

CR 


CH, 


-NCH, 

chloride  of  fenchyl    alcohol 


Crude  camphene  also  contains  a  very  small  amount  of  p-pinolene 
or  tricyclene.  It  will  be  noted  that  the  fenchyl  chloride  or  the  cor- 
responding alcohol  whose  structure  is  shown  above  cannot  lose  HC1 
or  water  to  form  a  double  bond  with  either  of  the  adjacent  carbon 
atoms.  But  Quist  made  tricyclene  by  decomposing  the  methyl  xan- 
thate  ester  of  fenchyl  alcohol  and  therefore  shares  Aschan's  views  as 
to  the  nature  of  tricyclene  and  its  method  of  formation, 


H 


Tricyclene  is  stable  toward  alkaline  permanganate  but,  as  with 
most  cyclopropane  structures,  acids  rupture  the  3  carbon  ring  and 
the  Bertram- Walbaum  reaction  accordingly  gives  the  acetate  of  iso- 
fenchyl  alcohol.  Hydrogen  chloride  at  — 10°  yields  a  hydrochloride 


Ann.  887,  24   (1912). 


BIG YC LIC  NON-BENZENOID  HYDROCARBONS 


509 


melting  at  27.5°  to  29°,  which  on  decomposition  forms  a  fenchene 
boiling  at  154°.  Tricyclene  itself,  as  purified  by  Aschan  by  oxidizing 
the  accompanying  fenchenes  by  permanganate,  boils  at  141.5°-143.5.° 
Fenchenes  or  tricyclene  contained  in  the  crude  camphene,  employed 
for  the  manufacture  of  artificial  camphor,  will  accordingly  be  con- 
verted to  fenchyl  and  isofenchyl  alcohols  which  will  in  turn  be  oxi- 
dized to  the  corresponding  ketones.  The  relations  of  these  substances 
are  probably  as  follows, 


CH, 

fenchyl  alcohol 


CH, 

p-pinolene 
(tricyclene) 


CH3 
isofenchyl 
alcohol 


CH3 

isofenchone 


As  regards  the  purification  of  synthetic  camphor  for  industrial 
purposes,  it  should  be  noted  that  manufacturers  of  celluloid  usually 
specify  that  the  chlorine186  content  shall  not  exceed  0.1  %  and  borneol 
should  not  be  present  in  excess  of  0.5  per  cent.  For  some  grades  of 
celluloid  a  melting-point  of  165°  is  sufficient  but  for  high-grade  ma- 
terial the  melting-point  should  not  be  lower  than  174°.  A  saturated 
solution  in  95  per  cent  alcohol  should  show  no  yellow  color  and  when 
kept  in  ordinary  diffused  daylight  in  a  colorless  transparent  bottle  the 

186  For  the  quantitative  determination  of  chlorine  in  synthetic  camphor  the  method 
of  Drogin  and  Rosanoff  (J.  Am.  Chem.  Soc.  38,  711  [1916]),  or  that  of  Van  Winkle 
and  Smith  (J.  Am.  Chem.  Soc.  42.  333  [1920])  is  recommended.  The  per  cent,  of 
borneol  may  be  determined  by  acetylating  with  acetic  anhydride,  in  the  usual  manner, 
and  determining  the  saponification  number  of  the  product ;  borneol  or  isoborneol  mny 
also  be  separated  from  camphor  by  the  phthalic  anhydride  method. 


510       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

camphor  should  not  become  visibly  discolored  in  30  days.  Nitro 
derivatives  are  very  apt  to  cause  the  development  of  a  yellow  color. 
The  presence  of  nitro  derivatives  also  causes  the  formation  of  a  slight 
tarry  or  resinous  residue  when  a  few  grams  of  the  camphor  are  sub- 
limed slowly  from  a  watch  glass.  The  chief  impurities  encountered 
in  commercial  natural  camphor  are  camphor  oil,  water  and  mineral 
matter. 

As  regards  the  yields  of  synthetic  camphor  obtained  in  industrial 
practice  there  are  naturally  no  reliable  published  data.  Schmidt187 
gives  the  following  yields:  solid  bornyl  chloride  43  per  cent,  camphene 
from  bornyl  chloride  95  per  cent,  isobornyl  acetate  from  camphene 
86  per  cent,  saponification  to  isoborneol  98  per  cent,  oxidation  of  iso- 
borneol  to  camphor  about  80  per  cent,  or  a  net  yield  from  the  original 
turpentine  of  24  per  cent  of  the  theory.  Austerweil 188  gives  the  yield 
of  crystalline  bornyl  chloride  as  55  to  60  per  cent  and  Ullman189 
gives  55.3  per  cent  of  the  theory  as  the  yield  of  the  chloride.  Accord- 
ing to  the  writer's  experience  these  yields  are  too  low,  particularly  as 
regards  bornyl  chloride,  which  with  reasonable  skill  can  be  obtained 
in  yields  of  75  to  78  per  cent  of  the  theory,  and  the  acetylation  of 
camphene  can  be  relief  upon  to  give  a  yield  of  isobornyl  acetate  cor- 
responding to  92  to  94  per  cent  of  the  theory.  The  net  yield  of  cam- 
phor should  be  45  to  50  per  cent  of  the  theory.  Methods  for  the 
synthesis  of  camphor  which  are  of  theoretical  interest  are  discussed 
in  connection  with  the  constitution  of  camphor. 

""Chem.  Ind.  29,  241   (1906). 
"'German  Pat.  211,799    (1908). 
"•Enzykl.  techn.  chem.  Ill,  257. 


Chapter  XIV.     Cyclic  Non-benzenoid 
Hydrocarbons. 

Cycloheptane,  Cyclooctane,  Cyclononane  and  Polynaphthenes. 

Cycloheptane  and  its  derivatives  are  difficult  to  prepare  and  have 
been  comparatively  little  studied.  The  ketone,  cycloheptanone 
(suberone) ,  is  the  material  most  frequently  employed  for  the  prepa- 
ration of  other  cycloheptane  derivatives  and  Willstatter  has  used  the 
cycloheptatriene  (tropilidene)  formed  by  the  exhaustive  methylation 
and  decomposition  of  tropidine,  and  also  cycloheptatriene  from  anhy- 
dro-ecgonine.  Eucarvone  has  also  been  employed  in  the  preparation 
of  other  cycloheptane  derivatives. 

The  physical  properties  of  cycloheptane,  cycloheptene,  cyclohep- 
tadiene  (hydrotropilidine)  and  cycloheptatriene  (tropilidine)  are  as 
follows,1 

0° 
Boiling-Pomt  d  0°  nD 

Cycloheptane  117.  °-117.5°  0.8253 

Cycloheptene    114.5°-115.  °  0.8407 

A1-3-cycloheptadiene    120.  °-121.  °  •     0.8810  1.495997 

A1 ''''-cycloheptatriene    116.  °(corr.)  0.9083  1.5175 

Cycloheptane  was  made  by  Markownikow2  from  cycloheptanone 
by  reducing  the  ketone  to  cycloheptanol  (suberyl  alcohol)  and  reduc- 
ing the  corresponding  bromide  by  zinc  dust  and  alcohol.  Willstatter 
and  Kametaka  3  reduced  cycloheptadiene  (hydrotropilidene)  by  Saba- 
tier  and  Senderens'  method,  at  180°.  The  cycloheptane  made  under 
these  conditions  is  quite  pure  but  at  235°  further  hydrogenation  to 
normal  heptane  occurs  and  at  250°  this  change  is  quite  rapid.  Cyclo- 
heptanol cannot  be  reduced  to  cycloheptane  by  heating  .with  hydri- 
odic  acid,  methylcyclohexane  being  formed.* 

The  formation  of  a  hydrocarbon,  C7H8,  by  distilling  methyltropine- 

1  Willstatter,   Ann.   317,   204    (1901). 

'Ann.   327,  59    (1903). 

•Ber.  41,  1480   (1908). 

•Markownikow,  J.  prakt.  Chem.   (2)  49,  430  (1894). 

511 


512       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

methyl  iodide  was  observed  by  Ladenburg,  and  Merling5  obtained 
the  hydrocarbon  by  exhaustive  methylation  of  tropidine  and  decom- 
posing the  tertiary  ammonium  hydroxide  by  heat.  The  conversion  of 
tropinic  acid  to  normal  pimelic  acid  led  to  the  view  that  the  tropine 
bases  and  their  nitrogen  free  decomposition  products  possessed  a 
cycloheptane  ring  and  that  tropilidine  and  hydrotropilidine  were 
cycloheptatriene  and  cycloheptadiene  respectively.  Willstatter  con- 
firmed this  by  synthesizing  both  hydrocarbons. 

Cycloheptene  can  readily  be  prepared  by  decomposing  cyclo- 
heptyl  iodide  in  the  usual  manner,  and  the  addition  of  bromine  gives 
1 . 2-dibromocycloheptane,  but  when  the  dibromide  is  heated  with 
quinoline  two  bromine  atoms  are  removed,  not  two  molecules  of  hydro- 
bromic  acid,  the  resulting  product  being  cycloheptene,  not  the  expected 
diene.  Alcoholic,  caustic  potash  converts  the  dibromide  into  the  un- 
saturated  ether,  and  similarly,  heating  the  dibromide  with  dimethyl 
amine  forms  a  dimethyl  amino  derivative, 

CH2  —  CH2  —  CHBr  CH2  —  CH2  —  CH .  N  (CH3)  2HBr 


\  +  2NH(CH3) 


CHBr 


\ 


CH 


I2  _  CH2  —  CH2  CH2  —  CH2  —  CH 

By  adding  methyl  iodide  to  the  resulting  base  and  decomposing  the 
tertiary  ammonium  hydroxide  by  heat,  Willstatter  made  A1-3-cyclo- 
heptadiene,  which  proved  to  be  identical  with  hydrotropilidene 

H 

CH2  —  CH2  —  CN(CH3)3.OH  CH2  — CH  =  CH 

CH  — ->  CH. 

CH2  —  CH2  —  CH  CH2  —  CH2  —  CH 

Willstatter  also  made  A1-3-cycloheptadiene  in  another  manner.6 
From  the  decomposition  products  of  cocain  A1-cycloheptenecarboxylic 
acid  was  obtained,  which  was  treated  with  hydrogen  bromide  to  form 
2  bromocycloheptanecarboxylic  acid,  which  was  decomposed,  losing 

"Ber.  24,  3109  (1891).     The  cycloheptane  ring  is  bridged  in  the  following  manner, 
CH2  — CH  — CH2 

NH  >  CHa  (tropane). 

f*TT    ,       f*TT  -      I^TT 

•Einhorn  &  Willstatter,  Ann.  280,  136  2(1894). 


BICYCLIC  NON-BENZENOID  HYDROCARBONS 


513 


HBr  to  form  a  mixture  of  the  A1  and  A2  acids.  The  A2  acid  was  sepa- 
rated by  fractional  crystallization;  converted  to  the  amide,  and  the 
latter~"treated  with  bromine  and  alkali  (Hofmann's  reaction)  to  form 
the  amine,  from  which,  by  the  method  of  exhaustive  methylation,  the 
conjugated  diene  was  made. 


•CH, 


•CH; 


•CH: 


The  addition  of  bromine  to  A1-3-cycloheptadiene  takes  place  in 
accordance  with  the  general  rule  of  the  addition  of  bromine  to  con- 
jugated dienes,  to  form  1 . 4-dibromo-A2-cycloheptene,  which  by  heat- 
ing with  quinoline,  loses  2  molecules  of  hydrogen  bromide  to  form 
cycloheptatriene 


CH2  — CH  =CH 


CH 


Br, 


CH 


—  CH2  — CH 


CH 


Br 

—  CH  — CH 
\ 


CH 


)H2  — CH2  — CH.Br 


CH  =CH  —  CH 
\ 


/ 


CH 


Cycloheptatriene  resinifies  rapidly  in  contact  with  the  air  and  follows 
generally  the  behavior  of  conjugated  dienes. 

Tetramethylcycloheptatriene  was  made  by  treating  eucarvone  with 
magnesium-methyl  iodide.7     It  is  not  definitely  known  whether  the 


'Rupe  &  Kerkcvius,  Ber.  U,  2702  (1911). 


514       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

third  double  bond  is  in  the  ring  or  semicyclic.  The  physical  proper- 
ties of  the  hydrocarbon  are  as  follows,  boiling-point  67°-67.5°  (11 
mm.),  d 20o  0.8687,  nD  1.5066,  MD  50.70,  EMD  1.33.  Its  constitu- 
tion may  be  inferred  from  the  constitution  of  eucarvone  (q.v.).  It  is 
very  little  changed  by  boiling  with  10  per  cent  sulfuric  acid.  Reduction 
by  sodium  and  ethyl  alcohol  yields  a  diene,  CuE^,  distilling  at  64.5°- 
65.5°  (12mm.). 

Diazoacetic  ester  combines  with  toluene  and  the  xylenes  to  form 
derivatives  of  norcaradienecarboxylic  acid.  Thus  when  toluene  and 
diazoacetic  ester  are  boiled  together  (copper  powder  as  a  catalyst  is 
not  necessary)  nitrogen  is  rapidly  evolved  and  3-methylnorcara- 
dienene-7-carboxylic  ester  is  formed.  Para-xylene,  treated  in  the 
same  way,  yields  the  bicyclic  ester,  and  this  ester  can  be  treated  in 
several  ways  to  break  the  3-carbon  ring.  The  first  condensation 
product  is  regarded  by  Buchner  and  Schulz  8  as  the  ethyl  ester  of 
2.5-dimethyl-A2-4-norcaradienenecarboxylic  acid.  By  heating  the 
amide  to  160°-170°,  or  heating  the  crude  condensation  product  with 
15  per  cent  sulfuric  acid,  or  by  heating  with  water  at  160°-170°,  the 
3-carbon  ring  is  broken,  forming  chiefly  2.5-dimethyl-A2-5-7-cyclohep- 
tatriene-7-carboxylic  acid,  melting-point  136°-137°. 
CH3 

CH=:C  — CH 

..CH.C02C2H5 
=  C  —  CH 

CH3      --jo 

When  the  A2-5-7  acid  is  reduced  by  sodium  amalgam  two  atoms  of 
hydrogen  are  added  forming  what  Buchner  regards  as  the  A-5  acid, 
melting-point  of  the  crude  acid  38°-40°,  but  too  unstable  to  purify. 
Obviously  a  number  of  isomeric  acids  containing  two  double  bonds  are 
possible,  and  by  adding  hydrogen  bromide  to  the  A2-5  acid  and  then 
removing  HBr  by  the  action  of  alkali,  Buchner  obtained  an  isomeric 
acid  melting  at  82°,  which  he  regards  as  the  A2-6  acid.  Reduction  by 
hydrogen  and  platinum  black  yields  2 . 5-dimethylcycloheptanecar- 
boxylic  acid,  an  oil  at  ordinary  temperatures  (amide  melting  at  185°- 
186°). 

•Ann.  378,  259   (1910). 


BICYCLIC  NON-BENZENOID  HYDROCARBONS  515 

Goldsworthy  and  Perkin  9  made  trans.  1  .  2  .  4  .  -cycloheptanetri- 
carboxylic  acid  by  the  latter's  well-known  method  of  synthesis,  using 
sodium  ethylate  as  a  condensing  agent, 

C(XC2H5 
CH2  —  CH(C02C2H5)2  CH2  —  CH< 

CH9Br  CH2 

C 
HBr  CH  —  CO,C2H6 


CH2  +    |       —  *   CH 

CHBr 

CH2-CH(C02C2H5)2 

C0CH     C 


H2  — CH 

C02C2H5 

The  ester  was  saponified  by  alcoholic  caustic  potash  in  the  usual 
manner,  the  free  acid  melting  at  198°-200°. 

Cycloheptanone,  the  raw  material  most  frequently  employed  for 
preparing  cycloheptane  derivatives,  may  be  prepared  by  heating  the 
calcium  salt  of  suberic  acid.10  When  purified  by  means  of  the  semi- 
carbazone  or  the  bisulfite  compound  and  regenerating  the  ketone,  it 

21  5° 
has  the  following  physical  properties,  boiling-point  180°,  d — 1—0.9498, 

nD  1.46027,  MD   32.35  (calculated  32.34) ." 

Cycloheptanone  forms  a  dibenzylidene  derivative, 

C7H80.(CH.C6H5)2, 

melting  at  107°-108°,  and  like  cyclopentanone  and  cyclohexanone, 
forms  a  series  of  well  crystallized  compounds  with  other  aldehydes 
(with  anisaldehyde,  melting-point  128°-129° ;  with  cinnamic  aldehyde, 
melting-point  198°;  with  piperonal,  melting-point  137°).  It  con- 
denses with  acetone  but  with  much  greater  difficulty  than  the  lower 
cyclic  homologues.12  Like  other  cyclic  ketones  the  oxime  is  rear- 
ranged by  sulfuric  acid  to  the  so-called  isooxime, 
CH2  —  CH2  —  CH2  —  CO 

CH2  —  CH2  —  CH2  —  NH 

This  isooxime  is  readily  split  by  heating  with  hydrochloric  acid  to 
amido-n-heptylic  acid.  The  ketone  reacts  normally  in  the  Grignard 
reaction,  for  example,  with  magnesium-methyl  iodide  to  form  1-meth- 

9J.  Chem.  Soc.  105,  2675    (1914). 
10Wislicenus  &  Mager,  Ann.  275,  357    (1893). 
"Auwers,  Ann.  410,  283  (1915). 
"Wallach,  Ann.  394,  366   (1913). 


516       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

ylcycloheptanol-(l),  which  in  turn  readily  decomposes  to  kl-methyl- 

cycloheptene,  boiling-point  137.5°-138.5°,  d1ft  _0  0.824,  n^    1.4581 

iy.o  D 

The  reactions  of  this  hydrocarbon  are  parallel  to  those  already  dis 
cussed;  for  example,  it  forms  a  nitrosochloride  (melting-point  106C 
which  on  heating  with  dimethylaniline  yields  the  unsaturated  oxime 
which  in  turn  may  then  be  hydrolysed  by  dilute  acids  to  the  unsatu 
rated    ketone    A1-2-methylcycloheptene-3-one     (boiling-point    200°- 
205°,  d0  0.9695). 


CH  —  Cu 


t— CH, 


XH 


, 
CH,r— CH, 


•CHt— CM 


VCH 


/ 
CH— CH, 


-CH,— C^ 
-CH,— CH, 


-CH,— C; 


.NOH 


\ 


;C-CH, 


CH, — CH 


CHZ — CO 
-CH2 CH 


C-CH, 


It  also  condenses  with  bromo-acetic  ester  in  the  presence  of  zinc  to 
give  cycloheptanol  acetic  acid,  from  which  Wallach  13  obtained  meth 
enecycloheptane  in  the  usual  manner.  Methenecycloheptane  dis- 
tills at  138°-140°,  d  0.824,  n  1.4611.  This  hydrocarbon  under- 
goes reactions  strictly  parallel  with  those  which  have  already  been 
discussed  in  connection  with  other  hydrocarbons  having  the  methene 
>C  =  CH2  group,  for  example,  on  oxidation  it  forms  a  glycol  (melt- 
ing-point 50°-51°)  which  is  converted  to  cycloheptane  aldehyde  by 
heating  with  dilute  acids. 

Kotz  14  has  studied  the  chlorination  and  bromination  of  cyclohep- 
tanone  and  finds  that,  like  cyclohexanone,  the  halogen  enters  the 
ring  in  the  CH2  group  adjacent  to  the  carbonyl  group,  these  facts 
harmonizing  with  the  view  that  the  ketone  reacts  with  the  halogen  in 
the  enol  form,  adding  C12  or  Br2  and  subsequently  splitting  off  a  mole- 
cule of  halogen  acid.  The  chloroketone  is  much  more  stable  than  the 
bromoketone.  The  chloroketone  is  not  hydrolyzed  by  aqueous  caustic 
potash  at  ordinary  temperatures  but,  on  warming,  the  corresponding 
oxyketone  is  formed  (yield  poor) .  Oxyketones  of  this  type  show  most 
interesting  properties;  neither  the  oxyketone  nor  its  methyl  ether 
forms  an  oxime  and  the  methyl  ether  may  readily  be  prepared  by 

»  Ann.  Slit,  158  ;  3^5,  146. 
"Ann.  400,  47  (1913). 


B1CYCLIC  NON-BENZENOID  HYDROCARBONS  517 

saturating  the  methyl  alcohol  solution  by  hydrogen  chloride,  like  the 
esterification  of  a  carboxylic  acid.  The  unsaturated  ketone,  A2-cyclo- 
heptenone,  was  reduced  by  Kotz,  by  Paal's  method,  to  cycloheptanone, 
confirming  Willstatter's 15  constitution  for  this  ketone  (tropilene). 

Eucarvone:  When  carvone  combines  with  one  molecule  of  hydro- 
bromic  acid  and  is  then  treated  with  alkali  to  remove  HBr,  the  result- 
ing ketone  proves  to  be  an  isomer  of  carvone.  Baeyer,  the  discoverer 
of  the  reaction,  regarded  eucarvone  as  bicyclic  having  a  cyclopropane 
ring  although  he  himself  pointed  out  several  objections  to  such  a 
structure.  Dihydroeucarvone  and  tetrahydroeucarvone  he  regarded 
as  derivatives  of  cycloheptanone.  Further  objections  to  Baeyer 's  con- 
stitution for  eucarvone 

CH3 


H2C  CH  eucarvone  (Baeyer) 

C 
H\ 

C(CH3) 


were  pointed  out  by  Wallach,  who  prepared  a  condensation  product 
with  benzaldehyde,  clearly  indicating  the  presence  of  the  — CH2 — CO — 
group.  Also,  when  prepared  from  optically  active  carvone,  eucarvone, 
according  to  Baeyer's  constitution,  should  be  capable  of  optical 
activity,  but,  as  Baeyer  himself  observed,  it  is  inactive.  Reduction 
of  eucarvone  by  sodium  gives  dihydroeucarvone  and  a  little  tetra- 
hydroeucarvone, but  by  catalytic  hydrogenation  in  the  presence  of 
palladium  tetrahydroeucarvone  is  readily  produced,16  a  method  of 
reduction  which  practically  precludes  rearrangements.  Baeyer  had 
already  shown  that  tetrahydroeucarvone  was  a  derivative  of  cyclo- 
heptanone,  being  oxidized  in  the  following  manner, 


CH2  —  CH2  —  CH2  CH2  —  CH2  —  CH2 


\ 


CH-CH 


\ 


CO-CH 


CH,  —  C — CH,  —  C  =  0     CH,  -  C  —  OH,  —  C00H 


CH3  CH3        keto  acid. 

18  Per.  44,  465  (1911).     Others  considered  tropilene  to  be  tetrahydrobenzaldehyde. 
"  Wallach,  Ann.  SS9f  107  ;  S81,  67. 


518       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

by  Ca  salt         CH2  —  CH2  —  CH2 


CH2  —  CH2  —  CH2 


CH3  — 


C09H. 


CHa- 


CH,  — CO 


CH2  — C02H 


fifi-dimethylpimelic  acid 


dimethylcyclohexanone. 


Wallach  therefore  explains  the  behavior  of  eucarvone  by  the  foH 
lowing  formula,  the  bicyclic  ketone  assumed  by  Baeyer  evidently  be- 
ing an  unstable  intermediate  product, 

:H, 


CH 

hydrobromocarvone 


unstable  intermediate  eucarvone 

product  (Wallach) 


The  reduction  by  sodium  indicates  that  the  two  double  bonds  in 
eucarvone  are  in  the  conjugated  position,  but  the  constitution  of  the 
dihydro  derivative  is  not  definitely  known,  although  the  reduction 
probably  follows  the  partial  valence  rule  of  Thiele,  leading  to  the 
following  constitution  for  dihydroeucarvone. 


HC 


CH3 

C 


HC          CH2 
HC  -  C(CH3) 


„          OH, 

HC          C  =  0 
HC          CH2 

H2C C(CH3) 

dihydroeucarvone  ? 


BICYCLIC  NON-BENZENOID  HYDROCARBONS  519 

Eucarvone  has  the  following  physical  properties,  boiling-point  85°- 

20° 
87°   (12  mm.);  d     0  0.952,  n  — -1.5048.18    Its  semicarbazone  melts 

at  183°-185°,  the  oxime  at  106°  and  the  benzylidene  compound, 
fprmed  by  its  reaction  with  benzaldehyde,  melts  at  112°-113°.  By 
partially  hydrogenating  the  oxime  of  eucarvone  Wallach  19  discovered 
the  oxime  of  a  dihydroeucarvone,  which  is  not  identical  with  that 
previously  known,  and  Wallach  accordingly  distinguishes  the  two 
known  dihydroeucarvones  as  a  and  |3,  the  latter  being  the  newly 
discovered  one. 

Oxime       Semicarbazone 
B.P.  d  M.P.  M.P. 

21° 


205°  0.9215  liquid  189°-191° 

213°-214°        0.9325        122°-123°        195°-197° 


Tetrahydroeucarvone  has  the  following  physical  properties,  boiling- 
point  207°,  d  0.906,  n.^  1.4553;  it  yields  a  semicarbazone,  obtained 

in  two  forms  one  melting  at  201°  and  the  other  at  161°-163°;  the 
oxime  is  an  oil  when  made  from  the  saturated  ketone  but  when  made 
by  the  catalytic  hydrogenation  of  eucarvoxime,  melts  at  56°-57°, 
the  further  reduction  of  which  yields  tetrahydroeucarvylamine. 

Cyclooctane:  Just  as  tropin  may  be  oxidized  to  tropinic  acid  and 
to  normal  pimelic  acid,  pseudopelletierin  may  be  oxidized  to  suberic 
acid.  The  alkaloid  from  pomegranate  root  therefore  contains  a  cyclo- 
octane  ring,  in  fact,  as  Ciamician  and  Silber,20  and  Piccinini 21  have 
shown,  the  alkaloid  contains  the  bridged  ring 

CH2-       -CH-       -CH2 
CH2  N.CH3       CO 

CH2-       -CH-       -CH2 

By  exhaustive  methylation  of  the  base,  adding  methyl  iodide  to 
cfes-dimethylgranatanine  and  decomposing  the  free  tertiary  ammo- 
nium hydroxide,  Willstatter  and  Veraguth 22  obtained  a  cycloocta- 
diene.  The  octadiene  polymerizes  so  readily  that  when  distillation 
was  attempted  polymerization  occurred  at  130°-150°,  with  almost 

18  Wallach,  loc.  cit. 

19  Ooett.  Nachr.   1913,  246. 

™Ber.  26,  156,  2738    (1893)  ;  27,  2850   (1894)  ;  29,  490,  2970    (1896). 
21  Gazz.  chim.  ItcU.  29   (2),  104    (1899). 
MBer.  S8t  1976   (1905). 


520      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

explosive  violence,  to  a  resinous  mass  and  resinification  takes  place 
rapidly  on  standing  in  contact  with  air.  At  16.5  mm.  it  distills  at 

0°  ^ 

39.5°,  d  —  0.889.    It  has  a  very  penetrating,  unpleasant  odor  and 

inhalation  of  the  vapors  readily  produces  headache.  It  reacts  readily 
with  nitric  acid,  dissolving  completely.  On  standing  the  hydrocarbon 
is  converted  to  a  dimeride  which  may  be  crystallized  out  by  strongly 
cooling,  the  crystals  melting  at  114°.  Bromine  reacts  with  the  hydro- 
carbon very  energetically  even  at  — 10°  in  chloroform  solution,  some 
hydrobromic  acid  being  evolved.  When  the  dihydrobromide  is  de- 
composed by  heating  with  caustic  alkali  or  quinoline,  a  new  octadiene 
is  formed,  distilling  at  143°-144°  and  characterized  by  a  very  pleas- 
ant odor,  and  almost  no  tendency  to  polymerization.  The  former 
cyclooctadiene  has  properties  very  strikingly  similar  to  those  of 
cyclopentadiene  and  Willstatter  accordingly  regards  the  first  diene  as 
having  the  double  bonds  in  conjugated  positions,  i.  e.,  A^-cyclo- 
octadiene.  The  more  stable  cyclooctadiene,  evidently  A1-4  or  A1-5, 
is  smoothly  reduced  by  Sabatier  and  Senderen's  method  to  cyclo- 
octane,  boiling-point  146.3 °-148°.  Cyclooctane  is  stable  to  per- 
manganate but  is  oxidized  by  nitric  acid  to  suberic  acid. 

When  the  unstable  diene,  a-cyclooctadiene,  is  treated  with  hydro- 
bromic acid,  the  dihydrobromide  formed  is  always  accompanied  by 
a  saturated  monohydrobromide,  from  which  a  bicyclic  octene  is 
formed  by  heating  with  quinoline.  This  bicyclic  hydrocarbon  distills 

0° 
at  138°-139°,  d—  0.9097.     Its  constitution  is  not  definitely  known; 

by  carefully  oxidizing  with  permanganate  a  crystalline  a-oxyketone 

CO 

is  formed,  C6H10<| 

CHOH. 

The  yield  of  cyclooctanone  obtained  by  heating  the  calcium  salt 
of  azelaic  acid  is  very  poor.  The  ketone  distills  at  195°-197°,  melt- 
ing-point 25°-26°. 

By  distilling  the  barium  salt  of  p-vinylacrylic  acid  Doebner23 
has  obtained  a  cyclooctadiene  boiling  at  50°-52°  (17mm.)  which  he 
regards  as  A1-5-cyclooctadiene.  Sorbic  acid  treated  in  the  same 
way  yields  S^-dimethyl-A^-cyclooctadiene,  boiling-point  68°-71° 
(15mm.). 

By  decomposing  the  tetrabromide  of  the  more  stable  or  |3-cyclo- 

"Ber.  35,  2129   (1902)  ;  Ber.  40,  146   (1907). 


BICYCLIC  NON-BENZENOID  HYDROCARBONS  521 

octadiene,  Willstatter  24  obtained  cyclooctatetrene.  Cyclooctatetrene 
has  been  of  interest  because  of  the  fact  that  it  possesses  none  of  the 
properties  characteristic  of  the  benzenoid  hydrocarbons.  It  readily 
combines  with  4  molecules  of  hydrogen,  reduces  permanganate  and 
absorbs  bromine.  With  nitric  and  sulfuric  acid  nitrating  mixtures, 
it  yields  resin  but  no  nitro-  derivatives.  Its  structure  is  therefore  to 
be  represented  as  follows: 


/  \ 

HC  CH 


H 


e 


Willstatter,  who  discovered  the  substance,  accordingly  states  that 
benzene  cannot  have  the  structures  indicated  by  the  Kekule  constitu- 
tion. No  indication  of  the  existence  of  a  more  stable  form  was  ob- 
tained and  Willstatter,  favoring  the  Armstrong  and  Baeyer  constitu- 
tion for  benzene,  considers  that  in  the  case  of  an  eight  carbon  ring 
centric  equilibrium  of  the  fourth  valence  of  each  carbon  atom  is  not 
established  because  the  distance  of  the  carbon  atoms  from  the  center, 
or  from  opposite  carbon  atoms,  is  greater  than  in  the  case  of  benzene. 

As  might  be  surmised  from  the  properties  of  the  fulvenes,  noted 
above,  cyclooctatetrene  is  a  yellow  oil  of  very  powerful  odor,  oxidizes 
rapidly  in  contact  with  air  and  readily  polymerizes. 

Cyclononane  :  Calvi  25  attempted  to  prepare  cyclononanone  by 
heating  the  calcium  salt  of  sebacinic  acid  but  without  success,  and 
later  Petersen  26  attempted  the  same  preparation  but  noted  a  very 
complex  decomposition,  identifying  benzene,  propionic  aldehyde  and 
heptane  aldehyde  among  the  products.  Dale  and  Schorlemmer  2T 
noted  the  formation  of  a  hydrocarbon  C16H32  distilling  at  283°-285°, 
under  similar  conditions.  Zelinsky  28  obtained  only  20  grams  of  a 
ketonic  substance  from  2  kilos  of  sebacinic  acid,  from  which  he  pre- 
pared the  semicarbazone  and  regenerated  the  ketone  in  the  usual 

oo  5° 
manner.    The  ketone  distills  at  95°-97°   (17-18  mm.),  d  _  —0.8665. 

Zelinsky  reduced  the  ketone,  with  sodium  and  moist  ether,  to  the 
alcohol  which  he  converted  to  the  iodide  and  reduced  the  latter  by 

14  Willstatter  &  Waser,  Ber.  44,  3423   (1911). 
"Ann.  91,  110   (1854). 
"Ann.   103,  184    (1857). 
"Ann.  199,  149   (1879). 
»Bvr.  40  ,  3278   (1907). 


522       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

zinc  dust  in  acetic  acid.  The  quantity  of  the  hydrocarbon  made  by 
Zelinsky  was  evidently  too  small  for  great  reliance  to  be  placed  upon 
its  physical  constants  and  inferences  drawn  therefrom. 

According  to  Windaus  29  cholesterol  contains  a  bicyclic  nine  carbon 
atom  ring,  having  obtained  evidence  of  a  ring  of  the  character  indi- 
cated by  the  following  partially  elucidated  formula, 


CH9 CH9 CH CH 


2 CH2 CH.CH  = 

Polynaphthenes:  Lubricating  oils  of  the  general  empirical  for- 
mula CnH2n  =  2  and  CnH2n=4  are  generally  believed  to  be  poly  cyclic 
hydrocarbons  although  there  is  no  direct  evidence  of  their  constitu- 
tion other  than  the  empirical  formula  and  inferences  drawn  from 
their  physical  properties  such  as  viscosity  and  their  not  crystallizing 
at  low  temperatures.  Such  oils,  even  when  repeatedly  distilled  and 
fractions  separated  within  very  narrow  temperature  limits,  are  un- 
doubtedly very  complex  mixtures  and  the  great  difficulty  of  separat- 
ing pure  substances  from  even  simpler  mixtures  has  already  been 
pointed  out.  The  task  of  determining  the  constitution  of  such  hydro- 
carbons, assuming  it  to  be  worth  while,  would  be  an  almost  impossible 
one  and  probably  not  worth  the  enormous  effort  required. 

When  formaldehyde  or  para-formaldehyde  is  heated  with  tetra- 
hydronaphthalene  and  phosphorus  pentoxide,  a  highly  viscous  oil  it? 
obtained,  boiling  at  257°-258°  (15mm.).  A  brittle  resin  is  also 
formed.  The  oil  has  been  proposed  as  a  lubricant  and  its  process  ot 
manufacture  patented.30  Heusler  and  Engler 31  observed  the  poly- 
merization of  light,  low-boiling,  unsaturated  hydrocarbons  to  poly- 
naphthenes  of  the  lubricating  oil  type,  by  heating  the  former  hydro- 
carbons under  pressure.  It  is  quite  possible  that  the  lighter  unsaturated 
hydrocarbons  found  in  shale  oil  distillates  could  be  polymerized  by 
such  a  process,32  or  by  treating  with  anhydrous  aluminum  chloride, 
to  more  stable  polymers  of  the  lubricating  oil  type;  in  fact,  such  u 

"Ber.  53,  488  (1920). 
80  German  Pat.  333,060;  319,799. 
slBer.  28,  490    (1895)  ;  30,  2358,  2365    (1897). 

12  Phenols  and  organic  acids  present  in  crude  shale  oil  naturally  destroy  the 
efficacy  of  the  aluminum  chloride,  unless  removed. 


BICYCLIC  NON-BENZENOID  HYDROCARBONS  523 

process,  using  aluminum  chloride,  has  already  been  carried  out  indus- 
trially in  the  United  States,  polymerizing  the  low-boiling  olefines  made 
by  cracking  (such  olefines  being  largely  lost  by  the  usual  refining 
process),  to  lubricating  oils  of  good  quality. 

In  the  absence  of  scientific  information  regarding  the  chemical 
constitution  of  lubricating  oils,  a  great  many  claims  are  sometimes 
made  for  the  supposed  excellence  of  certain  oils,  or  rather  commercial 
brands.  As  pointed  out  by  Dunstan  and  Thole  33  "It  appears  beyond 
doubt  that  the  high  boiling  fractions  of  petroleum,  irrespective  of 
their  place  of  origin,  are  complex  mixtures  containing  a  very  small 
percentage  of  paraffine  hydrocarbons  of  the  formula  CnH2n  2,  and  con- 
sisting chiefly  of  compounds  whose  formula}  range  from  CnH2n  to 
CnH2n-8."  This  is  true  even  of  so-called  paraffine  base  oils  of  the 
light  Pennsylvania  type. 

The  nature  of  the  unsaturated  hydrocarbons  in  lubricating  oils 
is  an  open  question.  They  show  large  losses  on  treating  with  con- 
centrated sulfuric  acid,  these  losses  amounting  to  20  to  40  per  cent; 
they  show  indefinite  iodine  numbers  but  attempts  to  hydrogenate  such 
oils  have  been  negative.  Treatment  with  liquid  sulfur  dioxide  results 
in  a  partial  separation.  Thus,  an  oil  showing  an  iodine  number  of 
46  gave,  after  extraction,  a  residue  of  iodine  number  33  and  an  ex- 
tracted portion  having  an  iodine  number  of  73.  Somewhat  similar 
results  are  effected  by  fullers'  earth. 

As  previously  pointed  out,  the  usual  methods  of  determining  iodine 
numbers  are  of  little  value  for  lubricating  oils.  Thus  Dunstan  and 
Thole  state  that  the  reaction  of  mineral  oils  toward  iodine  differs 
profoundly  from  that  of  fatty  oils.  According  to  their  experience 
with  the  Wijs  reagent,  by  varying  the  time  and  proportion  of  iodine 
chloride,  a  given  mineral  oil  may  yield  widely  varying  values.  For 
example,  a  California  mineral  oil  gave  a  value  of  20  in  2  hours,  40  in 
4  hours,  60  in  64  hours  and  80  in  266  hours,  whereas  rape  oil  reached 
a  steady  value  in  three  minutes.  Again,  the  iodine  value  of  rape  oil 
was  found  to  be  practically  independent  of  the  amount  of  Wijs'  solu- 
tion used  (provided  a  fair  excess  was  employed)  but  with  a  mineral 
lubricating  oil  an  increase  in  the  proportion  of  reagent  to  oil  invariably 
augments  the  iodine  value. 

Highly  refined  oils  such  as  white  pharmaceutical  oil  are  inferior 
in  viscosity  and  lubricating  value  to  those  oils  which  are  less  highly 
refined  and  which  contain  a  certain  proportion  of  so-called  unsatu- 
rated hydrocarbons. 

M  J.  Inat.  Petr.  Techn.  7,  417  (1921). 


Chapter  XV.     Rearrangements 

Rearrangement  of  carbocyclic  structures  to  substances  having  a 
different  number  of  carbon  atoms  in  the  ring  is  occasionally  observed 
in  the  case  of  hydrocarbons  but  such  rearrangements  are  much  more 
frequently  noted  with  derivatives. 

On  strongly  heating  cyclohexane  under  pressure,  conversion  to 
methylcyclopentane  occurs  and  Markownikow x  showed  that  when 
cyclohexyl  chloride  or  iodide  is  heated  with  concentrated  hydriodic 
acid  methyl  cyclopentane  is  formed.  Pure  cyclohexane,  however,  is 
not  effected  by  heating  with  hydriodic  acid.  The  conversion  of  cyclo- 
heptyl  iodide  into  methylcyclohexane  and  dimethylcyclopentane  is  a 
reaction  of  very  much  the  same  kind.  Cyclobutylcarbinol  and  hydro- 
gen bromide  results  in  conversion  of  the  four  carbon  to  the  five  carbon 
ring,  namely,  to  cyclopentylbromide. 

Change  of  cyclobutane  derivatives  to  cyclopentane  derivatives  was 
noted  by  Kishner 2  on  heating  dimethyl  or  diethylcyclobutyl  carbinol 
with  oxalic  acid. 


CH 


2J"1-5 


C.H.  C2H5 

/  CH2  — C< 

CH2  — CH  — C  — OH  /                   C,H 
\         +  HI  -H>  iodide  +  KOH  -n»CH2 

C2H6  \ 

[2-CH2  CH  = 

*Ann.  302,  1   (1898). 

'«/.  Rugs.  Phys.-Uhem.  Soc.  Jt2,  1211   (1910)  ;  45,  1149  (1911). 

524 


REARRANGEMENTS 


525 


CH2  — C< 


CKL  — 


CH2OH 


HBr. 


CH2  —  CH2 


The  change  of  the  four  carbon  ring  in  pinene  to  a  five  carbon  ring 
by  the  action  of  dry  hydrogen  chloride  forming  bornyl  chloride  is  a 
reaction  the  mechanism  of  which  is  obscure,  but  is,  nevertheless,  an 
illustration  of  the  tendency  of  four  carbon  atom  rings  to  rupture  or 
to  change  to  five  carbon  atom  rings.  Demjanow3  discovered  that 
cyclobutylmethylamine  is  converted  into  cyclopentanol  by  the  action 
of  nitrous  acid: 


H0C 


CHNH.CH, 


H2C CH2 


HONO 


H2C 


CH, 


H,C          C 


HOH 


\ 


C 
H 


Cyclobutylamine  and  nitrous  acid,  however,  yield  a  mixture  of 
eyglobutanol  and  cyclopropylcarbinol. 

H2C  -  CHNH2 

+  HONO  -  > 


HC 


H. 


CH, 


\ 


CH2OH. 


\ 


H. 


Cyclopentylmethylamine  and  nitrous  acid  readily  yields  cyclo- 
hexanol  and  in  the  same  way  cyclohexylmethylamine  is  converted 
into  cyoloheptanol.* 

Conversion  of  the  cyclopentane  ring  to  the  cyclobutane  ring  has 
been  noted  by  Rosanov,  cyclopentyl  nitrite  being  converted  by  the 
action  of  concentrated  alkali  into  nitromethylcyclobutane.5 


CH,—  CH, 


H 


CH2  — C< 


CH3 


H,  — CH 


N(X 


•J.  Chem.  Soc.  1910,  I,   838. 
•Wallach,  Ann.  353,  331    (1907). 
•J.  Chem.  Soc.  Aba.  1915,  I,  657. 


526       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


Dehydration  of  cyclopentylcarbinol  by  oxalic  acid  yields  cyclo- 
hexene,  which  Rosanov  considers  is  formed  with  the  intermediate 
formation  of  the  bicylic  hydrocarbon, 

K 


-CH 


CH 


Probably  influenced  by  his  studies  of  the  reactions  of  sabinene, 
which  contains  a  three  carbon  ring,  Wallach  has  offered  an  explana- 
tion of  these  reactions  based  upon  the  intermediate  formation  of  a 
cyclopropane  ring  'structure  as  indicated  by  the  following : 


CH2  —  CH, 


CH9  — CH 


CH.CH9NK 


/H2  — 


H0 


CH0 


CH, 


CH2  — 


CHOH 


CH, 
CH, 


It  is  curious  that  when  treated  with  hydrogen  bromide,  the  cyclo- 
propane ring  in  sabinane  is  broken  in  such  a  way  that  the  five  carbon 
ring,  not  the  six  carbon  ring,  is  preserved.6 


HB. 


Tiffeneau 7  observed  change  of  the  cyclohexane  ring  to  the  cyclo- 
pentane  ring,  when  2-iodocyclohexanol  is  treated  with  silver  nitrate. 

•Kisbner,  J.  Russ.  Phys.-Cliem.  Soc.  43.  1157   (1911). 
"'Cornet,  rend.  159,  771   (1914J. 


REARRANGEMENTS 


627 


CH3 


HO 


When  cyclic  a-monochloroketones  are  treated  with  alcoholic  caus- 
tic potash,  cyclic  acids  result  in  which  the  number  of  carbon  atoms 
in  the  ring  is  reduced  by  one.8  Thus  2-chlorocylohexanone  gives 
cyclopentanecarboxylic  acid,  and  4-chloro-l-methylcyclohexane-3- 
one  yields  methylcyclopentane-3-carboxylic  acid.  Favorski's  experi- 
mental work  does  not  show  that  the  carbon  atom  to  which  the  chlo- 
rine is  attached  is  the  one  which  becomes  the  carboxyl  group.  Wal- 
lach's  theory  of  the  intermediate  formation  of  a  bicyclic  compound  is 
applicable  to  this  case,  and  explains  the  function  of  the  alkali  which 
is  necessary  to  effect  the  change, 


CH  —  CH  —  CHC1 


CH  —  CH  —  C  = 


CH2  — CH2  — CH 
CH2  —  CH  — "C  =  O 


H0 


CH2 
H2 


^ 

1 


CH, 


CH 


CH, 


COOH. 


Wallach  has  reviewed9  the  rearrangement  of  dibromocyclic 
ketones,  particularly  cyclohexanones,  by  alkali  to  hydroxy  acids  of 
one  less  number  of  carbon  atoms  in  the  ring.  As  a  rule  the  two 
halogen  atoms  are  substituted  not  on  the  same  carbon  atom  as  >  CBr2 
but  each  halogen  replaces  a  hydrogen  atom  of  the  two  adjacent  carbon 
atoms.  Wallach  assumes  the  intermediate  formation  of  a  three- 
carbon  ring  derivative  leading  to  the  formation  of  an  ortho-diketone. 
Such  diketones  when  isolated  appear  to  have  changed  to  the  ketol, 
like  buchu  camphor.  Both  menthone  and  carvomenthone  give  dibro- 
mides  which  yield  the  same  cyclopentane  carboxylic  acid  derivative, 
which  Wallach  explains  as  follows, 

'Favorski  &  Boshovski,  J.  Bus*.  PJiys.-Chem.  8oc.  46,  1097   (1914). 
•Ann.  414,  296   (1918). 


528      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


In  a  study  of  the  Wagner  rearrangement  Ruzicka 10  obtained  evi- 
dence which  strongly  supports  the  theory  of  the  intermediate  forma- 
tion of  cyclopropane  derivatives  in  such  rearrangements.  As  regards 
the  intermediate  cyclopropane  theory  versus  the  theory  of  dissociation 
to  bivalent  carbon  Ruzicka  finds  that  rearrangement  takes  place  with 
tertiary  alcohols,  such  as  methyl  borneol  and  methyl  fenchyl  alcohol, 
which  could  not  yield  bivalent  carbon  directly  by  loss  of  water.  The 
products  of  dehydration  of  methylborneol  and  methylfenchyl  alcohol 
are  identical,  which  fact  Ruzicka  considers  to  be  in  confirmation  of 
the  tricyclene  or  cyclopropane  theory. 

Meerwein11  showed  that  l-isopropylcyclopentane-1.6-diol  is  con- 
verted by  the  pinacoline  rearrangement  to  the  six  carbon  ring  2.2- 
dimethy  1  cyclohexanone : 


CH2  — CH2 
CH2 —  CH2 


>c-c< 


CHa 
CH, 


H 


CH2  — CH2  — CO 
I  I       CH3 

CH2  — CH2  — C< 

CH3 


Further  work  showed  that  apparently, 

(1)  By  pinacoline  rearrangement  no  intermediate  products  of  the 
trimethylene  or  ethylene  oxide  type  could  be  detected  or  isolated. 

"Helv.  Chim.  Acta.  I.  110   (1918). 
"Ann.  S76,  152  (1910). 


REARRANGEMENTS 


529 


(2)  The  behavior  of  the  cyclic  pinacones  on  rearrangement  is 
essentially  a  special  case  of  the  general  rules,  holding  good  also  with 
acyclic  pinacones. 

(3)  The  course  of  the  pinacoline  rearrangements  is  determined  by 
different  factors  according  to  the  structure  of  the  pinacone.    In  the 
symmetrical  type 

\    /• 

C C 

/I  |\ 

R        OH      OH     Rx 

the  rearrangement  is  determined  by  the  ease  of  "migration"  of  the 
groups  R  and  Rx.    With  those  of  the  unsymmetrical  type, 
R  R 

"    -'•  "•"''  \-c 

R±        OH      OH     "R1 

the  relative   stabilities  of  the  two  hydroxyl  groups   are  more   im- 
portant. 

Meerwein  made  the  diethyl  and  diphenyl  derivatives  correspond- 
ing to  the  above  from  a-oxycyclopentane  carbonic  ester, 
CH2  —  CH2  CH2  —  CH2  R 

\C  —  C02CH3  +  2RMgBr  -*  \C  —  C  < 

CH2  —  CH2j 


CH 


-CH2()H 


OH 


The  diethyl  derivative  yields  the  two  pinacolines,  2 . 2-diethylcy clo- 
hexanone  and  1 . 1-ethylpropionylcyclopentane, 


CH2  — 


the  latter  in  largest  amount. 


n2 
L/xlj  —  (u  —  O 

_o 

CH2  —  C  —  C 

CA 

H2 

C2H5 

CH2  —  CH2 

1       > 

.CH2  —  CH2 

C2H5 

^" 
^. 

530       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

The  diphenyl  derivative,  however,  yields  the  six  ring  ketone  quan- 
titatively, 

•C*o 

m 

Tc< 

OH    OH 


-/ 
to 


The  as-diphenylpentamethylene  glycol,  however,  does  not  rear- 
range to  the  cycloheptanone  derivative  (as  might  be  expected  from 
Baeyer's  theory)  but  yields  chiefly  the  oxide. 


\ 


OH    OH 


The  dimethylpentamethylene  glycol  gives  the  two  ketones, 


CH 


OH  OH 


This  heptanone  derivative  was  overlooked  by  Tarbouriech.12 
Rearrangement  of  five  carbon  rings  to  six  carbon  rings  by  pina- 
coline   rearrangement  has   been   observed   previously.    Klinger   and 
Lonnes13  reduced  fluorenone  with  zinc  dust  and  acetyl  chloride  ob- 
taining not  the  expected  glycol  or  pinacone  but  the  ketone, 


C.H 


CO 


— c 


f/C.H4 
\»< 


"Compt.  rend.  11$,  605,  863    (1909)  ;  150,  1606   (1910). 
™£er.  29,  2154    (1896). 


REARRANGEMENTS  531 

Meerwein  shows  that  the  similarly  constituted  os-dimethyl  and 
as-diethyldiphenylene  glycols  yield  exclusively  the  normal  pinacoline, 
without  change  of  the  five  carbon  ring,  e.  g., 


The  diphenyl  derivative  is  converted  into  the  six  carbon  ring  of 
phenanthrene. 

The  same  explanation,  pinacoline  rearrangement,  explains  the 
result  noted  by  Klinger  and  Lonnes  on  oxidizing  diphenyldiphenylene- 
ethylene. 


CTT  f^    TT 

6^4  ^6^5 

C6H5  C6H4          COC6Ha 


V^gO-A^ 

| 
C6H4 


Theory  of  the  Pinacoline  Rearrangement:  The  assumption  of  in- 
termediate formation  of  a  triatomic  ring  was  made  first  by  Erlen- 
meyer,14  who  supposed  the  formation  of  substituted  ethylene  oxides. 
Under  special  conditions,  the  formation  of  ethylene  oxide  derivatives 
can  be  shown  in  the  case  of  benz-pinacone  and  sym.-diphenylditolyl- 
glycol:  these  particular  oxides  are  converted  into  ketones  on  heating 
with  dilute  mineral  acids.  Against  the  general  theory,  Meerwein  cites 
the  well-known  fact  that  the  oxides  are  usually  converted,  by  addition 
of  water,  to  glycols  under  much  milder  conditions  than  the  latter  are 
converted  into  pinacones,  recalling  particularly  the  case  of  tetra- 
metfiylethyleneoxide  which  takes  up  water  to  form  the  glycol  even 
in  the  absence  of  acids.  The  results  of  Tiffeneau 15  on  the  properties 
of  substituted  ethylene  oxides  also  support,  the  views  of  Meer- 
wein. 

Meerwein  assumes  that  in  diethyltetramethyleneglycol  both 
hydroxyls  have  approximately  equal  tendencies  to  split  off  as 
water,  therefore,  leading  to  the  formation  of  the  two  ketones, 
thus, 

"Ber.  14.  322   (1881).      (Cf.  also  Nef,  Ann.  198,  148  [1879]). 
chim.  phys.    (8)    10,  346,  375    (1905). 


532      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


In  the  conversion  of  borneol  or  isoborneol  to  camphene  with  loss 
of  water  the  1,2,3,4,8  pentamethylene  ring  is  converted  into  a  six 
carbon  ring,  and  the  original  six  carbon  ring,  1  to  6,  is  converted  into  a 
five  carbon  ring. 


©=CH, 


H,® 

y  H          H 

Wagner 16  in  his  original  camphene-borneol  article  called  attention 
to  changes  of  the  type, 
CH3 

CH3  —  C  —  CH  —  CH3  CH3  CH3 

CH3  OH  CH3  CH3 

and  for  which  Tiffeneau  suggests  the  name  "retropinacoline  rear- 
rangement." 17 

For  comparison  with  borneol  it  is  necessary  to  ascertain  the  dehy- 
dration behavior  of, 

(1)  Alcohols  of  the  cyclohexane  series,  hydroxyl  being  in  the  ring. 

(2)  Alcohols  of  the  cyclopentane  ring  in  which  the  hydroxyl  group 
is  in  the  side  chain,  for  example, 

18  J.  Ruaa.  Phys.-Chem.  Soc.  SI,  680   (1899). 
"Rev.  gen.  sci.  18,  583  (1907). 


REARRANGEMENTS 


533 


2 .2-dimethylcyclo-  1 .1-methyl-a- 

hexanol-1  oxethylcyclo- 

pentane 
In  splitting  off  water  from  I,  two  products  result,  as  indicated, 


—  about  75% 
^-isopropylcyclopentene  —  about  25% 

Instead  of  1 . 1-methyl-ct-oxethylcyclopentane,  Meerwein  employed 
its  derivative  3-isopropyl-l .  1-methyl-a-oxethylcyclopentane.18  As  in 
the  first  instance,  the  normal  product  of  dehydration  was  not  formed 
but  a  mixture  as  follows: 


,CH, 


"Ann.  Ifl5t  129  (1914) 


.  2-dimethyl-4-isopropyl 
fc-cyclohexene 
principal  product 


534       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


The  rearrangement  of  2.2-dimethylcyclohexanol-l  to  A1-isopro- 
pylcyclopentene,  with  decrease  in  the  carbon  ring,  C6  to  C5,  and  also 
likewise  the  ring  enlargement  by  rearrangement  of  3-isopropyl-l .  1- 
methyl-a-oxethylcyclopentane  to  1 . 2-dimethyl-4-isopropyl-A1-cyclo- 
hexene,  C5  to  C6,  is  completely  analogous  to  the  rearrangement  of 
borneol  to  camphene. 

This  is  made  clearer  by  writing  the  change  as  follows: 


jG 


/H 


CH. 


II 


rl 


or 


or 


The  conversion  of  borneol  to  camphene  is  practically  a  summary 
of  the  two  reactions  above. 

Clear  explanation  will  be  possible  probably  only  when  the  mecha- 
nism of  the  change  of  pinacoline  alcohol  to  tetramethylethylene  is 
clear.  Zelinsky  and  Zelikov,19  like  Nef,  suppose  the  formation  of  a 
trimethylene  ring. 

CH3  CH3  CH3 

>C  — CH  — CH3 >  >C  =  C< 

CH3      \/  CH3  CH3 

CH2 

This  explanation  has  been  given  for  the  borneol-camphene  change 
but  as  pointed  out  by  Semmler 20  the  hypothetical  intermediate  hydro- 
carbon 

18  Ber.  84,  3251    (1901). 

20  Ber.  85,  1018  (1902)  ;  Lipp,  Ber.  53,  769  (1920),  considers  that  the  reactions  of 
tricyclenic  acid  support  Semmler's  constitution  for  tricyclene. 


REARRANGEMENTS 


535 


is  completely  symmetrical  and  the  resulting  camphene  should  there- 
fore be  optically  inactive,  which  generally  is  not  the  case. 

Tiffeneau  21  has  suggested  that  water  is  split  off  from  pinacoline 
alcohols  as  follows: 

CH3       H         OH  CH3 

\  \/  \  \/  CH3  CH3 

CH3—  C  —  C  —  CH3  -»  CH3  —  C-C-CH3  -»  >C  =  C< 

/  /  CH3  CH3 

CH3  CH3 

Meerwein  22  succeeded  in  making  the  desired  1  .  1-methyloxethyl- 
cyclopentane  as  follows: 


CH—  CH, 


CH,— CH, 


Ci 


CH3 


acid 
chloride 


CH(OH)CH3 


By  warming  with  ZnCl2  water  is  readily  removed.     Of  the  three 
possibilities, 


CH3 


II  would  undoubtedly  be  rearranged  to  IV. 

III  and  IV  are  known.    The  substance  obtained  proved  to  be  very 


21  Rev.  gen.  act.  18,  583   (1907). 
28  Ann.  417,  255   (1918). 


536       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

nearly  pure  1 . 2-dimethyl-A1-cyclohexene,  or  III,  boiling-point  135°- 

20°  20° 

137°;  d 0.8234;  n —  1.4566.     Oxidation,  gave  2,7-diketooctane, 


D 
CH2 

H, 


CR 
CH, 


COCH3 
COCH, 


Meerwein  has  obtained  additional  results,  parallel  to  those  pre- 
viously noted,  in  the  case  of  1,2,2,3-tetramethyl-l.a-oxethylcyclopen- 
tane,  which  gives,  partly  with  ring  enlargement  and  partly  with  a 
rearrangement  of  a  methyl  group,  l^S^-pentamethyl-A^cyclo- 
hexene  and  l,2,2-trimethyl-3-isopropyl-A3-cyclopentene. 

CH3         CH3 

\/ 

CH,  —  CH  —  C  —  C  —  CH, 


CH, 


CH, 


CH3  —  CH  —  C  CH  (OH) .  CH, 

I  >C< 


CH2 — CH 


\ 


CH 


CH2  -  CH 
CH3 


J! 


CH, 


\     CH3CH  — C  CH3 

C  — CH 

CH2-CH  CH3 

Wallach  has  described  the  conversion  of  a  series  of  cyclohexanone 
derivatives  into  cyclopentanones.23  When  cyclohexanone  is  bromi- 
nated  in  acetic  acid  l,3-dibromohexane-2-one  is  formed,  which,  on 
treating  with  dilute  aqueous  caustic  potash  at  room  temperature, 
yields  an  acid  derivative  of  cyclopentanone.  On  treating  the  latter 
with  lead  peroxide  and  sulphuric  acid  cyclopentanone  itself  is  formed. 


28  J.  Chem.  Soc.  Ala.  J916,  I,  487. 


REARRANGEMENTS 


537 


Similar  reactions  were  carried  out  with  methylcyclohexanones  and 
in  the  case  of  menthone,  l-methyl-3-isopropylcyclopentane-2-one  was 
formed. 

CH3 

CH  CH3 

H2C          CH2  HoC CH 


H9C 


H,C 


=  0 


Chapter  XVI.     Physical  Properties 

With  the  exception  of  a  comparatively  small  number  of  hydro- 
carbons of  the  terpene  series,  the  physical  properties  recorded  in  the 
literature  of  the  non-benzenoid  hydrocarbons  differ  so  widely  in  each 
case  that  it  is  very  difficult  to  draw  any  general  conclusions  of  value 
from  data  at  present  available.  Simple  derivatives  of  the  hydro- 
carbons are  frequently  known  in  much  purer  condition  and  the  physi- 
cal properties  determined  with  much  greater  accuracy  than  in  the 
case  of  the  parent  hydrocarbons  themselves.  The  tables  of  physical 
properties  of  the  simpler  paraffine  hydrocarbons  shown  in  the  accom- 
panying tables  show  the  wide  disagreement  in  physical  constants  of 
these  simple  hydrocarbons.  The  figure  given  in  the  literature  for  the 
melting-point  of  normal  octane  is  — 98.2°  but  recent  determinations 
by  Forcrand  *  show  that  the  melting-point  of  normal  octane  is  —  57.4°. 
Very  few  of  the  unsaturated  hydrocarbons  derived  from  paraffine 
hydrocarbons  are  known  in  a  state  of  purity  and  the  constitution  of 
many  of  them  are  still  in  doubt.  Most  of  the  individuals  of  this 
series  described  thus  far  are  very  evidently  mixtures  of  two  or  more 
hydrocarbons. 

Density  and  Molecular  Volume:  The  density  of  individual  hydro- 
carbons is  frequently  given  at  temperatures  other  than  zero  degrees, 
4°,  15°,  17%°  or  20°  and  it  is  frequently  desirable  to  recalculate  the 
density  from  the  temperature  stated  to  some  standard  temperature, 
usually  zero  or  20°,  for  the  purpose  of  comparison.  Walden  has  shown 
that  the  increase  in  molecular  volume  VM  for  each  degree  Centigrade 

is  about  0.11  per  cent 2  the  molecular  volume  V  M  being  equal  to  the 

molecular  weight  divided  by  the  density. 

The  molecular  volumes  of  the  normal  paraffines  at  0°  show  an 
average  increment  for  CH2  of  15.9.3 

lCompt.  rend.  172,  31    (1921). 
2  Z.  physik.   Chem.  65,  158    (1909). 

*  Kauffmann,  Beziehungen  zwischen  physikalische  Eigenschaften  u.  chemische  Con- 
stitution, 1920,  p.  60. 

538 


PHYSICAL  PROPERTIES 
Hydrocarbon  V  A 


Pentane   ............................... 

15.4 

Hexane  ................................     1275 

15.8 
Heptane  ...............................     143.0 

Octane    ................................     158.9 

16.0 

Nonane   ...............................     174.9 

15.9 

Decane   ................................     1905 

16.0 

Undecane    .............................     2065 

15.6 

Dodecane4    ............................    222.4 

16.5 

Tridecane  ..  ...........................    238.9 

15.8 

Tetradecane4    ..........................     254.7 

165 

Pentadecane    .......  .  ...................     27L2 

Hexadecane   ...........................     2875 

The  molecular  volumes  of  isomeric  hydrocarbons  show  slight  dif- 
ferences, for  example, 

v*°l 
VM 

C5Hu  n.pentane  '  ..............................  115.2 

"      isopentane8    .............................  116.4 

CaHu  n.hexane6  ...............................  130.5 

"      2-methylpentane  7    ........................  131.1 

"      2.2-dimethylbutane  T    .....................  132.8 

"      2.3-dimethylbutane  7    ..................... 

"      3-methylpentane  8    .......................  129.1 

The  octanes  show  only  very  slight  differences  in  molecular  volume, 
the  maximum  being  that  of  2  .  5-dimethy  Ihexane  and  the  minimum  that 

of  3  .  4-dimethy  Ihexane,9 

V15° 
VM~ 
maximum   ........................     163.5 

minimum    ........................     157.2 

n.  octane    .........................     161.7 

20° 
The  monochlorohexanes  also  show  only  slight  differences  for  V  —  - 

«  Apparently  the  observed  specific  gravities  of  these  two  hydrocarbons  at  0°  are 
too  low  by  about  0.0009. 

'Timmennans.   Chem.  Zentr.  1912   (2),  472. 

•Auwers  &  Eisenlohr,  Z.  physik.  Client.  83,  431  (1913). 

'Kishner,  J.  Russ.  Phys.-Chem.  8oc.  tf,  595   (1911)  ;  47,  1111   (1915). 

"Kishner,  J.  Rus*.  Phys.-Chem.  Soc.  45,  973  (1913). 

•Clarke,  «7.  Am.  Chem.  Soc.  S3,  520   (1911)  ;  34,  170,  674   (1912). 


£40      CHEMISTRY  OF  THE  NON-BENZENOlD  HYDROCARBONS 

Maximum,  2-chloro-2-methylpentane   ...................     139.7 

Minimum,  3-chloro-3-methylpentane,  ...................     136.4 

n.hexyl  chloride   ...........................     137.7 

The  molecular  volumes  and  densities  of  the  hydrocarbons  of  the 
ethane  and  propane  series  have  been  determined  by  Maas  and 
Wright.10 

R  p  Difference 

D.-r.  A  T/ 

Hydrocarbon  °C  dR  V  V  M     VfV'M      $ 

Experimental  Calcul. 


Ethane 

—  883 

05459 

5495 

55 

0044 

Propane    

...      —44.5 

0.5853 

75.2 

77 

—  18 

0033 

Ethylene   

...     —  103.9 

0.5699 

491 

44 

+  51 

0045 

Propylene   

...      _47.0 

0.6095 

68.9 

66 

+  2.9 

.0034 

Acetylene   

...      —  83.6 

0.6208 

41.9 

33 

+  8.9 

.0046 

Allylene    . 

—  27.5 

0.6785 

59.0 

55 

+  4.0 

.0027 

dg    densities  at  the  boiling-points. 

V,,  molecular  volumes  calculated  from  dR 

V'-..  molecular  volumes  calculated  on  the  basis  C  =  2H  =  11. 

AV 

___r=the  tempertaure  coefficients  of  the  specific  volume  at  the 

AV 
boiling-point.    The  values  —--  are  dependent  upon  the  critical  tem- 

peratures of  the  hydrocarbons,  which  fact  makes  it  possible  to  calculate 
the  specific  volumes  of  any  of  the  hydrocarbons  at  any  temperature, 
provided  the  specific  volume  at  any  one  temperature  is  known  and 
the  specific  volumes  for  one  of  the  other  hydrocarbons  is  known  at  all 
temperatures.  This  was  one  of  the  deductions  made  by  van  der  Waals 
from  his  equation  of  corresponding  states,  namely  that 


where  Vj.  and  V2  are  the  specific  volumes  of  one  liquid  and  Vj  and  v2 
are  the  specific  volumes  of  another  liquid  where  V±  v±  and  V2  v2  are 
measured  at  the  same  corresponding  temperatures.  Taking  propylene 
as  a  standard  Maas  and  Wright  calculated  the  specific  volumes  of 
ethane,  ethylene,  acetylene,  propane  and  allylene  at  a  temperature  30° 
higher.  The  greatest  observed  discrepancy  between  the  calculated 
and  experimental  values  was  only  0.3%,  in  the  case  of  propane,  the 
other  cases  being  within  the  experimental  error  of  0.1%. 

10  J.  Am.  Chem.  8oc.  1$,  1105   (1921). 


PHYSICAL  PROPERTIES  541 

Ring  closing  usually  has  a  greater  effect  on  the  molecular  volume 
than  a  double  bond  or  branched  chain  structure,  as  compared  with 
normal  carbon  chain  structures. 

121 

V  M 

CaHw,     n.hexane  ......................................  130.5 

CeH12,     a-hexene11    ....................................  126.0 

ft-hexene     .....................................  123.3 

cyclohexane    ...................................  108.1 

propylallyl  ether  ...............................  125.1 

§-hexylene  oxide  1 

Clt-CH^CH-CHal  .......................  1146 

CEk—  CH,—  0 

allyl  ether  .....................................  119.3 

cyclohexanone    .................................  101.9 

methylbutyl  ether  .............................  118.4 

pentamethylene  oxide   .........................  97.4 

Cyclohexane  is  thus  seen  to  have  a  greater  density  than  n.hexene 
but  the  true  effect  of  ring  closing  on  the  molecular  volume  is  realized 
by  correcting  for  the  volume  of  the  two  hydrogen  atoms  difference 
between  C6H14  and  C6H12.  When  the  value  32.05  for  these  two  hy- 
drogen atoms  is  substracted  from  the  molecular  volume  of  hexane, 
130.5  —  32.05  =  98.4,  the  result  is  lower  than  the  observed  value  of 
cyclohexane  by  9.7  units.  The  molecular  volume  of  the  saturated 
cyclic  hydrocarbons  may  be  calculated  in  another  manner,  i.  e.,  by 

20° 

multiplying  the  value  for  CH2  at  20°,  V  —  -=  16.27,  by  the  number 

of  such  groups  in  the  hydrocarbon.  The  results  show  that  in  all  cases 
the  molecular  volume  of  the  cyclic  hydrocarbons  is  materially  greater 
than  the  values  corresponding  to  the  number  of  CH2  groups  present. 
The  latter  method  is  designated  as  II  and  the  former,  deducting  32.05 

20° 

from  the  V-^-oi  the  normal  hydrocarbons,  is  method  I  in  the  follow- 

M 

ing  table. 

T,20°  ,  Excess  of  observed 

HYDROCARBON"  V^-Cobs.)       oyer  caicuiated  values 

/  11 

Cyclobutane,  C4H«    .....................  81.7  16.6 

Cyclopentane,  C8HW   ....................  94.1  10.9  12.7 

Ccyclohexane,  CeH^  ...........  .  ........  108.1  9.7  10.5 

Cycloheptane,  C7H14  ....................  121.1  6.6  72 

Cyclooctane,  C8H16  ......................  133.7  3.1  3.5 

Cyclononane,  C,^  .....................  163.9  17.4  17.5 


"v.  Braun,  Ann.  382,  22   (1911). 

12  Cf.  values  given  by  Willstatter,  Ber.  40,  3988   (1907)  ;  p,  1483  (1908)  ;  4Sf  1182 
(1910). 


542      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

It  might  have  been  expected  from  Baeyer's  strain  theory  that  the 
closest  agreement  between  the  calculated  and  observed  molecular 
volumes  would  be  in  the  case  of  cyclopentane  and  cyclohexane,  instead 
of  cyclooctane.  The  same  order  of  differences  are  observed  in  the 
case  of  the  ethyl  derivatives. 

Effect  of  ring  closing; 

excess  of  observed 
20°  20° 

Hydrocarbon  V  -^-  over  calc.V  jj- 

Ethyl  cyclopropane13   103.3  20.2 

Ethyl  cyclobutane " 115.5  17.1 

Ethyl   cyclohexane15    143.1  12.5 

Ethyl  cycloheptane 16 154.8  8.2 

The  ketone  derivatives  show  the  same  order  of  differences,  the 
molecular  volume  at  20°  having  a  maximum  difference  from  the  cal- 
culated value  in  the  case  of  cyclobutanone,  minimum  in  the  case  of 
cyclooctanone  and  again  a  large  difference  in  the  case  of  cyclonona- 
none. 

The  effect  of  ring  closing  in  the  case  of  3 . 3-dimethylbicy  clohex- 
ane,17  considered  as  derived  from  0em.dimethylhexane  is  indicated  by 

20° 
a  difference  of  26.9  units.  V— — 138.3. 

M 

T.  W.  Richards  regards  the  relations  between  boiling-point  and 
density  as  a  natural  corollary  of  the  theory  of  atomic  compressibility 
or  deformability.  "Thus,  as  regards  two  substances  otherwise  similar, 
the  less  volatile  one  would  be  less  compressible,  denser  and  possess 
greater  surface  tension.  These  outcomes  of  the  theory  correspond 
with  the  facts  in  a  majority  of  cases  thus  far  studied;  for  example, 
o-xylene  is  denser,  less  volatile,  less  compressible  and  possesses  a 
greater  surface  tension  than  either  m-xylene  or  p-xylene."  18 

Tyrer  has  re-examined  Trouton's  rule  and  states  that  the  relation 
between  the  molecular  volume  and  boiling-point  may  be  better  ex- 
pressed by  a  modification  of  Trouton's  rule,  which  Tyrer19  formu- 
lates as  follows, 

"Zelinsky,  B&r.  46,  170   (1913). 

"Kishner,  «/.  Russ.  Phys.-Chcm.  Soc.  45,  973   (1913). 

'"Lebedew,  J.  Russ.  Phys.-Chem.  Soc.  43,  1124    (1911). 

18  Markownikow,  Ann.  327,  73   (1903). 

"Zelinsky,  Ber.  46,  1466  (1913).  In  his  monograph,  Kauffmann  makes  use  of 
Zelmskys  supposed  spirocyclane,  which  Philipow,  J.  prakt.  Chem.  93,  162  (1916),  has 
shown  to  be  a  mixture  of  methylcyclobutene  and  methenecyclobutane ;  Kauffmann's 
inferences  are  accordingly  incorrect 

"«/.  Ohem.  Soc.  99,  1211   (1911). 

*»PW.  Mag.   (6)  W,  522   (1910). 


PHYSICAL  PROPERTIES  543 


in  which  the  constant  K  is  68  for  the  aliphatic  hydrocarbons  and 
ethers,  70  for  alkyl  chlorides  and  amines,  74  for  the  fatty  acid  esters 
and  bromides  and  79  for  aliphatic  iodides  and  aromatic  hydrocarbons. 
Like  most  such  rules  the  constant  is  subject  to  considerable  variation, 
for  example, 

Substance  T  VM  K 

Methyl  bromide  .  286.  58.2  73.8 

Ethyl  bromide    312.7  77.7  73.0 

Propyl  bromide   344.  972  74.8 

Isopropyl  bromide  333.  97.2  71.9 

Ethyl  chloride  285.2  71.2  68.8 

Propyl  chloride  319.2  91.4  70.9 

Isopropyl  chloride  309.5  93.6  68.2 

Chloroform    334.1  &4.5  76.1 

Carbon  tetrachloride 349.7  103.7  74.3 

Melting-Point. 

Ring  closing  has  a  much  more  pronounced  effect  upon  the  melting- 
point.  Langmuir  comments  upon  the  fact  that  the  physical  prop- 
erties of  nitrous  oxide  are  practically  identical  with  those  of  carbon 
dioxide  at  a  temperature  3°  lower,  but  that  the  freezing  points  of 
these  two  substances  are  in  marked  contrast  to  the  general  agreement, 
being  — 102°  for  nitrous  oxide  and  —  56°  for  carbon  dioxide.  He 
states  that  "This  fact  may  be  taken  as  an  indication  that  the  freezing- 
point  is  a  property  which  is  abnormally  sensitive  to  even  slight  dif- 
ferences in  structure.  The  evidences  seem  to  indicate  that  the  mole- 
cule of  carbon  dioxide  is  more  symmetrical,  and  has  a  slightly  weaker 
external  field  of  force  than  that  of  nitrous  oxide."  Organic  chemists, 
however,  in  studying  the  relations  between  structure  and  physical 
properties,  have  paid  much  greater  attention  to  boiling-points,  specific 
gravities  and  optical  properties.  Probably  on  account  of  the  fact 
that,  as  Langmuir  points  out,  the  freezing-point  is  so  sensitive  to  dif- 
ferences in  molecular  structure,  it  is  very  difficult  to  trace  simple  rela- 
tionships or  make  any  useful  generalizations.  Also,  since  most  of  the 
non-benzenoid  hydrocarbons  and  their  simple  derivatives,  of  which 
we  have  fairly  complete  knowledge,  are  oils  at  ordinary  temperatures, 
data  as  to  their  freezing-points  are  usually  lacking. 

Most  of  the  non-benzenoid  hydrocarbons  which  are  solid  at  ordi- 
nary temperatures  are  normal  paraffines,  and  of  these  none  of  their 
many  possible  isomers  are  known,  so  that  no  data  exist  from  which 


544      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 


to  draw  any  conclusions  as  to  the  effect  of  variations  in  structure  upon 
the  melting-point. 

The  melting-points  of  the  normal  paraffines  are  given  in  the  fol- 
lowing table,  in  which  it  will  be  noticed  that  the  increment  for  CH2 
is  irregular  in  the  lower  part  of  the  series  but  becomes  more  regular 
and  smaller  with  increase  in  molecular  weight.  The  melting-point 
of  n.heptane  given  is  probably  too  low. 


Melting-Point 


Hydrocarbon 20 

CH4 —184. 

C2Ha    —172. 

v^/sxis     ••••••••••••••••••••••  •"  "•  lot/. 

C4H10  —135. 

€5^ —130.8 

C6Hi4  —94.3 

CTHM  —97.1 

CsHw    —57.4 

/~l  TT  __  r-i 

CioH^  '.   '.'.'.'.V.'.'.'.V.'.V .'.'.'.'.'.  —32! 

CnH2 —26.5 


Ci2.H2a 
CisHzs 


C1BH32 

Cl6ll34 

Cn±iM 


CasHw 


C24H«> 


—  12. 
—  6.2 
+  5.5 
10. 
18. 
22.5 
28. 
32. 
36.7 
40.4 
44.4 
47.7 
51.1 
68.1 
70.5 


Boiling-Point 

°C 
—  164. 

—  84.1 

—  44.5 
—  0.1 

+  36.2 
68.9 
98.4 

125.8 

149.5 

173. 

194.5 

214.5 

234. 

252.5 

270.5 

287.5 

303. 

317. 

330. 


According  to  Tsakalotos 21  the  curve  connecting  the  melting-points  of 
the  normal  paraffines  is  fairly  regular  and  smooth  from  about  C16H34 
and  upwards  in  the  series,  and  agree  well  with  the  values  calculated 


from  the  formula  An  = 


85-0.01882  (n-1) 


where  An  is  the  difference 


between  the  melting-point  of  one  member  and  the  next  highest  in  the 
series  and  n  is  the  number  of  carbon  atoms  in  the  molecule  of  the 
hydrocarbon  the  lower  in  the  series  (of  the  pair) . 

20  Methane,  Moissan  &  Chavanne,  Compt.  rend.  1$,  409  (1905)  ;  ethane,  Ladenburg, 
Ber.  33,  638  (1900)  ;  propane,  Maas  &  Wright,  J.  Am.  Chem.  Soc.  $,  1100  (1921)  ; 
C4Hi0  to  CgHig,  Timmermans,  Chem.  Zentr.  1911  (2),  1015;  CgHao  et.  sea.  Krafft.  Ber.  15 
1687  (1882)  ;  19,  2218  (1886)  ;  21,  2256  (1888). 

21Compt.  rend.  1*3,  1235  (1906);  Forcrand  [Compt.  rend.  172,  31  (1921]  states 
that  the  simpler  normal  paraffines,  and  the  cyclic  hydrocarbons  C8  to  C»  follow  the  rule 
of  the  alternance  of  melting-points. 


PHYSICAL  PROPERTIES  545 

The  substitution  of  chlorine  causes  marked  rise  in  the  melting- 
point.22 

Melting-Point        Boiling-Point 

Substance                                          °C  °C 

CH4   .......................    —184.  —164. 

CHaCl  .....................    —103.6  —23.4 

CH2Cla   ....................      —96.7  +41.6 

CHCU    .....................      —63.3  61.2 

CC14   .......................      —22.95  76.7 

CH3CH3    ...................     —172.1  —84.1 

CHaCaCl  .................     —138.7  +12.5 

CHaCHCl,  .............  ....      —96.7  +57.3 

CH2C1.CH.C12   .............      —35.5 

CHC12.CC13  ................      —29.0  +161.9 

+187.  +189.6 


Unsaturation  usually  causes  a  marked  rise  in  melting-point,23  in 
the  case  of  hydrocarbons. 

Ethane    ..............     —172.1  Propane  ..............     —189.9 

Ethylene  .............     —169.4  Propylene  ............     —1855 

Acetylene   ............      —81.8  Allylene   .............    —104.7 

It  is  of  interest  to  note  the  very  great  differences  in  the  melting- 
points  of  the  following  pairs  of  isomers,  noting  that  the  differences  in 
boiling-point  are  by  no  means  so  large. 

Melting-  Boiling- 

Point  Point 

n.pentane,  CH3(CH2)3CH324  ...............     —130.8°  +365° 

tetramethylmethane,     (CHa^C  ............      —  20.  °  +9.5° 

n.  octane,  CH^CH^CIk26  .................      —57.4°  125.8° 

2.2.3.3.  tetramethylbutane  M    ...............     +  103.°-104.°  106.°-107.° 

(CH3)3C.C(CH3)3 

The  effect  of  ring  closing  upon  the  melting-point  is  to  raise  it  and, 
as  will  be  noticed  above,  the  boiling-point  is  also  raised. 

Melting-Point  Melting-Point 

n.hexane    ............      —  93.5°  n.  octane    .............      —  985° 

cyclohexane   ..........        +  6.4°  cyclooctane   ..........      +  11.5° 

22  Timmermans,   loc.  cit. 

23Maas  &  Wright,  J.  Am.  Chem.  Soc.  43,  1100    (1921). 
2*  Timmermans,  Chem.  Zentr.  1911   (2),  1015. 
26Forcrand,  Compt.  rend.  172,  31   (1921). 

CH, 

26  The  similarly   constituted  undecane,    (CH3)3C  —  C  —  C)CH3)3,   and   tetradecane, 

CH8 
CH3  CH3 

(CH8)3C  —  C  —  C  —  C(CH3)S    are    not    known    but,    by    analogy,    their    melting-points 

CH8  CH3 
would  be  much  higher  than  n.undecane  and  n.tetradecane. 


CH3 

S>r 

CH.CH3 

p*^ 

CH-  L 

Br 

CH3 

^>O 

CH.CH2CH 

^^> 

CH3      | 

L 

CH3 

CH3 

546      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

The  very  marked  effect  of  structural  differences  on  the  melting- 
point  is  well  illustrated  by  the  dibromohexanes.  Increase  in  the  num- 
ber of  methyl  groups,  and  proximity  of  these  methyl  groups  to  the 
bromine  or  other  negative  substituent  raises  the  melting-point  as 
compared  with  isomeric  derivatives,  for  example, 

CH3  —  CH  .  CH2CH2CH  —  CH3  melting-point  38.2° 

Br  Br  (n.isomers  are  liquid) 

melting-point  7° 


liquid 


>C  —  CH<  melting-point  24°-25° 

CH3     |  CH3 

CH3  CH3 

>C  -  C<  melting-point  169°-170° 

CH3      |  |      CH3  corresponding  dichloro, 

Br        Br  melting-pointlGO0 

CH3 

\  melting-point  187° 

CH3  —  C.CBr2CH3  corresponding  dichloro, 

/  melting-point  151° 

CH3 

Nitro  groups  similarly  placed  result  in  crystalline  derivatives,  for 
example, 

CH8  N02 

CH8  —  C  —  C  —  CH3  melting-point  173°-174° 

CH3  N02 

CH3  CH3 

>C  -  C<  melting-point  213°-214° 

CH3     |  |     CH3 

N02     N02 


PHYSICAL  PROPERTIES  547 

The  melting-point  of  the  latter  substance  is  higher  than  that  of  any  of 
the  dinitro  or  trinitro  benzenes.  Dinitroheptane  and  octane  of  sim- 
ilar structures  are  also  well  crystallized  substances, 

CH3  CH3 

>C CH2  —  C<  melting-point  81°-82° 

CH3      |  |      CH3 

N02  N02 

CH3  CH3 

>C CH2 .  CH2 C<  melting-point  124°-125° 

CH3     |  |      CH3 

N02  N02 

Closing  of  the  ring  raises  the  boiling-point  slightly,  as  a  com- 
parison of  butane  and  cyclobutane  and  a  number  of  their  derivatives 
indicates, 

Boiling-  Boiling-  Difjer- 

n.  butane  series          Point  °C             Cyclobutane  series  Point  °C  ence°C 

n. butane  —0.1            c. butane   +11,  +11- 

C4H9C1    +77.            C4HT.C1    85.  +8. 

CJLNH,  76.             C^T.NH,    81.  +5. 

C4H8.Br    100.             C.HT.Br    104.  +4. 

C4H9.OH   116.             C4H7.OH   122.5  +6.5 

C4HJ    131.             C4HT.I   138.  +7. 

186.             CiHi.COaH 195.  +9. 


When  the  two  series  of  hydrocarbons  of  three  to  eight  carbon 
atoms  are  compared,  the  cyclic  series  is  seen  to  have  consistently 
higher  boiling-points. 

Boiling-points  of  cyclic  and  normal  hydrocarbons. 

Boiling-  Boiling-  Differ- 

Normal  Point  °C                       Cyclic  Point  °C  ence°C 

Propane    —  44.5  Cyclopropane  —  35.                   +    9.5 

Butane    —  0.1  Cyclobutane    +11-                  + 10-5 

Pentane    36J2  Cyclopentane   49.                  + 12.8 

Hexane  68.9  Cyclohexane   81.                   +12.1 

Heptane"  98.8  Cycloheptane   117.2+.2 

Octane   1253  Cyclo-octane   145.  ±2          +19.4 

Among  observations  of  the  boiling-point  a  few  qualitative  gen- 
eralizations can  be  made,  for  example,  Wallach  28  has  noted  that  in  a 
series  of  isomeric  ketones  the  widest  separation  of  the  ketone  group 
and  the  alkyl  side  chain  gives  the  highest  boiling-point. 

"Forcrand,  Compt.  rend,  m,  31   (1921). 
38  Ann.  391,  183  (1913). 


548      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

The  effect  of  unsaturation  on  the  boiling-point  and  critical  tem- 
perature in  the  ethane  and  propane  series  has  recently  been  shown  by 
Maas  and  Wright.29  The  figures  given  in  the  fourth  column  show  that 
the  boiling-points  are  approximately  equal  fractions  of  the  critical 
temperatures,  when  figured  as  degrees  absolute. 

Mol.  Latent 
Boiling- 
Hydrocarbons 


Point  °C 


fjeat  Boiling-Point 

t  Evaporation        t 

C°  C. 

Ethane    .                        ...      —88.3                35.0  3800  0.60 

Ethylene    —103.9                   9.9  3510  0.60 

Acetylene    .       —83.6                 36.5  5150  0.61 

Propane —44.5                 95.6  4500  0.62 

Propylene    —47.0                92.1  4600  0.62 

Allylene   —27.5               127.9  5230  0.61 

The  critical  values  of  a  number  of  hydrocarbons  of  the  methane 
series  are  given  by  Young.33 

Crit.  Pressure  Grit.  Temp.        Grit.  Density 

Hydrocarbon  mm.Hg.  °C  Density  atO°/4° 

n  Pentane    .                                   25100  197.2  0.2323  0.64536 

Isopentane  25018  187.8  0.2343  0.63927 

n  Hexane  22510  234.8  0.2344  0.67703 

Diisopropyl 23360  227.3  0.2411  0.67948 

n  Heptane    .              20430  266.8  0.2341  0.70048 

n' Octane   .                                      18730  296.2  0.2327  0.71854 

Diisobutyl 18660  276.8  0.2366  0.71021 

Cyclohexane    30278  280.  0.2735  0.79675 

Benzene 36395  288.5  0.3045  0.90006 

Absorption  of  Light;  Color:  All  saturated  hydrocarbons  are  color- 
less but  show  selective  absorption  in  the  infra  red.30  Examination  of 
hexane,  cyclohexane  and  camphane  shows  no  well  defined  absorption 
band  in  the  ultraviolet  part  of  the  spectrum,  of  wave  lengths  greater 
than  185  \I\L,  but  ring  formation  seems  to  cause  a  shift  of  general 
absorption  toward  the  longer  waves.  Certain  recent  works31  state 
that  unsaturated  hydrocarbons  show  no  selective  absorption  in  the 
ultraviolet  but,  on  the  contrary,  ethylenic  hydrocarbons  show  definite 
absorption  bands  and,  in  the  case  of  the  doubly  conjugated  fulvenes, 
absorption  bands  occur  in  the  visible  part  of  the  spectrum,  these 
hydrocarbons  being  colored  yellow  to  orange.  The  aliphatic  defines 
isobutylene,  trimethylethylene,  hexylene  and  octylene  show  two  ab- 
sorption bands,  at  A230-X205  and  at  about  A180.32  The  presence  of 

29  Loc.  cit. 

*a8ri.  Proc.  Roy.  Soc.  Dublin  12,  374  (1910). 

"°  Coblentz,  Jahrb.  Radioakt.  k,  7   (1908). 

81  Watson,  Color  in  Relation  to  Chemical  Composition,  1918,  p.  66. 

82  Stark,  Steubing,  Enklaar  &  Lipp,  J.  Chem.  Soc.  Abs.  1913,  II,  363. 


PHYSICAL  PROPERTIES  549 

two  double  bonds,  not  in  conjugated  positions,  causes  an  intensifica- 
tion of  the  two  absorption  bands  observed  in  the  case  of  the  singly 
unsaturated  hydrocarbons,  as  in  diallyl  and  geraniolene.  Two  con- 
jugated double  bonds  as  in  isoprene,  2-3-dimethylbutadiene,  and  hexa- 
diene-(1.4)  show  a  shift  in  the  position  of  the  two  bands  of  about 
20  to  30  jxji,  toward  the  visible  spectrum,  and  an  intensification  of  both 
bands. 

Camphene  and  a-pinene  show  an  absorption  band  at  X204-U98. 
In  limonene  and  sylvestrene  the  head  of  the  absorption  band  is  about 
X185  but  in  the  case  of  a  and  (3-phellandrene  two  bands  are  clearly 
developed. 

Fulvene  is  a  yellow  oil  and  dimethylfulvene, 

CH=CH  CH3 

>C  =  C< 
=  CH  CH3 


WJLJ. 

in 


shows  three  well  developed  absorption  bands  with  heads  at  X370,  X258 
and  X207  respectively. 

A  hydrocarbon  of  the  empirical  formula  C15H22  and  containing 
four  double  bonds  has  been  described  by  Sherndall 34  as  having  an 
intense  blue  color  and  accordingly  named  azulene.  The  hydrocarbon 
combines  with  eight  atoms  of  hydrogen,  in  the  presence  of  colloidal 
palladium,  forming  C15H26.  The  hydrocarbon  is  probably  a  tricyclic 
sesquiterpene  perhaps  identical  with  a-gurjunene.  It  readily  com- 
bines with  picric  acid,  forming  black  needles  melting  at  118°.  The 
intensity  of  the  color  is  indicated  by  the  fact  that  0.064  g.  of  azulene 
in  1  liter  of  gasoline  is  matched  in  color  by  an  ammoniacal  copper 
sulfate  solution  containing  0.24  g.  copper  sulfate  per  liter.  The  very- 
exceptional  color  of  azulene  as  compared  with  the  fulvenes,  renders  the 
confirmation  of  Sherndall's  work,  and  particularly  the  purity  of  the 
material  employed,  very  desirable. 

The  absorption  spectra  of  cyclohexene  and  cyclohexadiene  are  of 
interest  on  account  of  the  fact  that  they  are  very  different  from  the 
absorption  spectrum  of  benzene.  The  first  two  hydrocarbons  show 
broad  bands  differing  greatly  from  the  groups  of  narrow  bands  of  ben- 
zene and  naphthalene.35 

Fluorescence:  No  non-benzenoid  hydrocarbons  are  known  which 
exhibit  fluorescence.  The  marked  fluorescence  of  petroleum  distillates 
is  undoubtedly  due  to  traces  of  substances  of  the  nature  of  chrysene, 

MJ.  Am.  Chem.  Soc.  37,  1537   (1915). 

"Stark  &  Levy,  Jahrb.  Radioakt.  10,  179  (1913)  ;  J.  Chem.  Soc.  Abs.  1913,  II,  366. 


550       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

fluorene  or  pyrene,  although  the  substances  which  cause  fluorescence  in 
these  oils  have  never  been  isolated  and  identified.  They  are  easily 
sulfonated  and  are,  therefore,  removed  to  a  large  extent  on  refining 
such  oils  with  concentrated  sulfuric  acid,  appearing  as  water-soluble 
sulfonic  acids.  It  has  been  suggested  by  Schulz  36  and  others  that  the 
blue  fluorescence  of  petroleum  distillates  is  due  to  colloidally  dis- 
persed particles  of  carbon,  sulfur  or  other  material  but  oils  which 
are  carefully  dried  and  filtered  are  optically  homogenous  under  the 
ultramicroscope  and  the  fluorescence  is  in  no  way  affected  by  an 
electrostatic  field.37  The  formation  of  such  fluorescent  material  is 
almost  universally  observed  when  organic  material  is  partially  car- 
bonized by  heat,  even  in  the  heating  or  "boiling"  of  linseed  oil.  The 
manner  in  which  "deblooming"  agents,  such  as  nitrobenzene  or  nitro- 
naphthalene,  suppress  this  property  is  not  known  but  it  is  probably  a 
purely  physical  phenomenon.38  Ether,  benzene  and  amyl  alcohol 
intensify  the  fluorescence  and  aniline  and  carbon  bisulfide  suppress 
it,  changing  the  blue  fluorescence  of  petroleum  oils  to  a  dull  faint 
green. 

Refractivity :  Refractivity  has  been  frequently  employed  as  an 
aid  in  determining  the  constitution  of  organic  compounds  and  the 
constants  of  a  great  many  substances  have  been  studied  and  correlated. 
Although  the  refractive  indices  of  most  organic  substances  fall  within 
the  range  1.30  to  1.70,  most  instruments  of  reputable  make  are  accu- 
rate to  the  fourth  decimal  place  and  only  a  few  drops  of  liquid  sub- 
stance are  required  for  the  determination.  However,  in  order  that  the 
molecular  refractivity  may  be  calculated,  it  is  necessary  to  know  the 
density.  It  is  assumed  that  most  of  the  readers  of  this  volume  are 
familiar  with  the  refractometer  and  it  will  suffice  to  recall  the  two 
formulae  for  molecular  refractivity  which  are  in  common  use,  the  n2 
formula  proposed  by  H.  A.  Lorentz  and  L.  Lorenz  39  in  1880  being  the 
one  most  frequently  employed. 

(1)  Derived  from  Gladstone  and  Dale    M  =  — -  m. 

d 

(2)  Lorenz  and  Lorentz,  M=    2       .—. 

The  Lorenz  and  Lorentz  formula  is  practically  independent  of  tem- 

«•  Petroleum,  5,  205. 

"Brooke  &  Bacon,  J.  Ind.  d  Eng.  CTiem.  6,  623   (1914). 

"Kauffmann,  Ann.  393,  1   (1912). 

"Wied.  Annalen.  9,  641;  u,  70    (1880). 


PHYSICAL  PROPERTIES  551 

perature  and  pressure.  When  the  refractive  index  is  accurately  deter- 
mined to  the  fourth  decimal  place,  the  molecular  refraction  of  sub- 
stances having  molecular  weights  of  about  100  will  be  accurate  within 
zb  0.2.  Gladstone  and  Dale 40  discovered  that  the  refractivity  of 
organic  substances  is  modified  by  the  manner  of  combination  of  their 
constituent  atoms ;  in  other  words,  refractivity  is  a  constitutive  prop- 
erty. The  study  of  refractivity  with  reference  to  chemical  constitu- 
tion has  been  developed  particularly  by  Briihl  and  Auwers.  Although 
the  values  for  the  group  CH2,  obtained  by  Briihl  and  Conradi  and 
Landolt,  agree  fairly  close,  Eisenlohr41  has  recalculated  this  value 
from  data  of  503  carefully  purified  substances,  with  the  results  shown 
in  the  following,  for  the  sodium  D  line. 


Hydrocarbons    

Number  of 
Substances 
66 

Mj, 

4624 

Aldehydes  and  ketones     

92 

4626 

Acids         .  .       

74 

4613 

Alcohols              .           

81 

4634 

Esters 

.     ...      190 

4605 

mean       4.618 

The  values  obtained  by  Conradi42  and  by  Eisenlohr  are  as  fol- 
lows: 

Element                                                  Na^  Na  ^ 

(Conradi)  (Eisenlohr) 

Carbon   .                                                                           2.50  2.418 

CH,   4.60  4.618 

H    1.05  1.100 

0,  as  in  >C  =  0  2.28  2511 

O,  as  in  ethers  1.68  1.643 

O,  as  in  —  OH 1.52  1.525 

Cl   5.99  5.967 

Br    8.92  8.865 

I   14.12  13.900 

Ethylene  bond                  >  C  =  C  <,  increment  1.733 

Acetylene  bond  —  C  =  C  — ,  increment  2.398 

The  exaltation  caused  by  an  ethylene  bond  was  computed  from 
observations  on  the  following  hydrocarbons, 

"PMJ.   Trans.  153,  323    (1863). 

41  Z.  physik.  Chem.  75,  585   (1910). 

42  Z.  physik.  Chem.  3,  210  (1889). 


552       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

Mol.Wt.       Boiling-Point  D  MD 

I  _  on0 

Amylene"    C5H10/      .......       70'08  34'  ^  °  °'64761F 


70'08  367°  °'6664  24'83 


_ 
Amylene"       «     /=  ......  \ 

Hexylene"  =  .......        84'10 

Hexylene" 

Octylene"    C8Hia/= 

40TT/=..  140.2  154.°  0.7720-^r          47.17 

Decylene44  doH2o/ 

Diallyl,  d.limonene  and  sylvestrene  were  also  used  by  Eisenlohr. 

Eijkman  46  estimates  that  the  exaltation  in  refractivity  of  ethylene 
bonds  increases  with  the  number  of  radicals  attached  to  the  doubly 
linked  carbon  atoms,  as  follows,47 

One  radical,  RCH  —  CH2  .......................  1.60 

Two  radicals,  RCH  =  CHR   ...................  1.75 

Three  radicals,  R2C  =  CHR  ....................  1.88 

Four  radicals  R2C  =  CR2  .......................  2.00 

Le  Bas48  has  noted  that  usually  introduction  of  methyl  groups 
into  ring  structures  produces  exaltation, 

(1)  In  trimethylene  ring  =0.39 

(2)  In  tetramethylene  ring  =  0.15 

(3)  In  cyclopentane  and  cyclohexane  ring  =  0.15 

In  cases  where  two  methyl  groups  are  in  the  1.1  or  1.2  positions 
this  exaltation  disappears. 

The  values  for  nitrogen  and  sulfur  also  vary  according  to  the 
manner  of  their  combination. 

Nitrogen49  NaD          Sulfur  n  NaD 

Hydroxylamines   ..............      2.48  Mercaptans    ...............       7.69 

Amines,  primary  ..............       2.45  Sulfides  ....................       7.97 

Amines,  secondary    ...........      2.65  Thiocyanates    ..............      7.91 

Amines,  tertiary  ..............       3.00  Bisulfides  ..................      8.11 

Nitrites,  aliphatic  .............       3.05 

Oximes,  aliphatic  ........  .  ____      3.93 

Nitro  Group," 

nitroparaffines   ............      6.72 

Benzenoid  derivatives  .....      7.30 

«Brtihl,  Ann.  200,  181   (1880). 

"Landolt  &  Jahn,  Z.  physik.   Chem.  10,  302    (1892). 

«BBriihl,  J.  prakt.  Chem.  (2)  49,  241   (1894). 

MChem.  WeekUad.  3,  706   (1906). 

47  This  is  by  no  means  an  infallible  rule  as  cases  are  known  in  which  substitution 
of  a  methyl  group  causes  a  decrease  in  refractivity  ;  for  example,  styrene  and  methyl- 
sty  rene,  cf.  Auwers  &  Eisenlohr,  J.  prakt.  Uhem.  (2)  82,  65  (1910). 

"  Trans.  Faraday  Soc.  13,  53   (1917). 
'Briihl,  Z.  physik.  Chem.  79,  1    (1912). 
>Bruhl,  Z.  physik.  Chem.  25,  647   (1898). 

"Price  and  Twiss,  J.  Chem.  Soc.  101,  1259    (1912). 


PHYSICAL  PROPERTIES  553 

Briihl 52  concludes  that  ring  closing  does  not,  of  itself,  affect  the 
molecular  refraction,  except  in  the  two  types  to  which  attention  has 
already  been  called,  i.  e.,  ethylene  and  cyclopropane.  The  agreement 
between  the  calculated  and  observed  molecular  refractivities  in  the 

cyclic  series  is  fairly  close.53 

M  M 

Observed  Calculated 

Cyclobutane    18.22  18.41 

Cyclopentane    23.09  23.01 

Cyclohexane    27.67  27.62 

Cycloheptane"    32.18  32.22 

Cyclooctane    36.58  36.82 

Cyclononane    42.36  .       41.61 

Attention  has  already  been  called  to  the  instability,  or  condition 
of  stress,  of  cyclopropane.  Ostling 55  has  examined  a  large  number  of 
cyclopropane  and  cyclobutane  derivatives.  The  following  values  are 
typical,  and  indicate  that  ring  closing  in  the  case  of  cyclopropane 
produces  an  exaltation  of  approximately  0.70  or  a  little  less  than  one 
half  that  produced  by  a  single  ethylene  bond. 

EXALTATION  OF  MOLECULAR  REFRACTTVITY  CAUSED  BY  RING  CLOSING; 
CYCLOPROPANES. 

Formula  Boiling-Point  Dl~ 


x_/ 

A 


/ CH  .  CHs  nno 

CHa     |  32.6°-  33.2°  0.6755^-  0  68 

\CH.CH3 

2>C  CH.CHa66    ,  37.5°  0.7052^°  0.92 

H2  4° 

CH2  -17  co 

>CH.CH2OH5T    123.3°  0.8995^-  0.71 

H2 

CH2  1QO 

>CH.CO2H56 183.2M84.C  1.0897 -^  0.68 

H2 
CH2  170 

>CHCHO5T    98.°  (737mm.)      0.9294-nr  0.90 

Ha 

CH2          CO2CH3  157° 

>C<  196.6°  1.1509-r^—  0.71 

H3          C02CH3 

Sabinane    156.2°-156.8°  0.8142^r  0.70 

Sabinene58    163.°-165.°  0.8422^-  1.36 

Carane59    49.°-50.°(9mm.)    0.8381  |p  0.93 

82  Cf.  Ber.  25,  1952   (1892)  ;  27,  1065   (1897). 

53  Cf.  Auwers,  J.  Chem.  Soc.  A6».  1918,  II,  343;  Ann.  422,  133  (1921). 

M  WillstHtter  &  Kametaka,  Ber.  $J,  1483   (1908). 

65  J.  Chem.  Soc.  101,  457   (1912). 

"Gustavson  &  Popper,  J.  prakt.  CJicm.   (2)    58,  458    (1898). 

"Demjanov  &  Fortunov,  Ber.  kO,  4397    (1907). 

"Auwers,  Roth  &  Eisenlohr,  Ann.  S7S,  275   (1910). 

M  Semmler  &  Feldstein,  Ber.  Jft,  384   (1914). 


554       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

The  effect  of  a  double  bond  in  a  conjugated  position  to  the  cyclo- 
propane ring  produces  increased  exaltation,  as  shown  by  sabinene, 
and  an  aldehyde  or  ketone  group  adjacent  to  the  cyclopropane  ring 
also  produces  a  definite,  though  slight  increase  in  exaltation,  as  is 
shown  by  cyclopropyl  formaldehyde,  exaltation  for  M  =  0.90.  Of 

the  following  three  ketones  I  and  II  show  increased  exaltation  while 
III,  in  which  the  carbonyl  group  is  not  conjugated  with  reference  to 
the  cyclopropane  group,  shows  the  average  exaltation. 


increment 
M     =  0.89 
D 


increment 
M     =  1.03 
D 


increment 

M     =  0.70  or  0.76 
D 


The  hydrocarbon  1,2,3,  £nme£%£cyclopropane  shows  the  abnor- 
mally large  increment  for  M^  of  1.37  which  harmonizes  with  the 

observations  of  Le  Bas  and  Eijkman,  noted  above,  as  to  the  effect 
of  methyl  groups.  Closing  of  the  ring  as  in  cyclopropane  has  no 
effect  upon  the  molecular  dispersion  but  the  conjugation  of  a  cyclo- 
propane ring  and  an  ethylene  bond  causes  an  increase  of  approxi- 
mately 10  per  cent. 

The  increment  in  molecular  refractivity  produced  by  the  cyclo- 
butane  group  is  smaller  and  is  influenced  somewhat  by  substituent 
groups,  as  in  the  case  of  cyclopropane  derivatives. 


PHYSICAL  PROPERTIES 


555 


EXALTATION  OF  MOLECULAR  REFRACTIVITY  CAUSED  BY  RING  CLOSING; 
CYCLOBUTANE  SERIES. 


Formula 


Boiling-Point 


Incre- 
ment  for  M 


CHa-CHaTO  0° 

10.°-11.°  0.703fr 

CH2  — CH, 

CHa  — CHaw 98.5°-99.°  0.9381-jp- 

CHa  —  C  =  0 

CHa-CH,-  [0.91592°: 

CH2"~C\OH    122.5084  15o 

0.9226^ 

CH2-CH2» 195.°  1.0570^ 

PTT      r/H 
U113  —  v-^c02H 

in  Q° 

CHa-CH,    157.°  0.9525^ 

CHa  — CH.C02C2H5 

20° 
CHa-CH,    104.°-105.°  1.0456^- 

I  «/C02C2H5«  12mm' 

CHa~U\C02C2H8 

17  3° 

CH2-CH.C02C2H5"  114.5°  1.1191-^- 

20mm. 
CHa  — CH.C02C2H8 

d.a  pinene  156.4°-156.6°  0.8594^1 

nopinone    .  118.2°  0.9827 

43mm. 


0.49 

0.42 
0.43 

0.46 
0.43 
0.37 

0.54 

0.46 
0.57 


«>  WillstStter,  Ber.  40,  3982   (1907). 
81Kishner,  J.  Russ.  Phys.-CJiem.  Soc.  STt,  106   (1905). 
«Briihl,  Ber.  S2,  1222    (1899). 
«Zelinsky  &  Gutt,  Ber.  40,  4744   (1907). 

"Demjanov  &  Doyarenko,  J.  Rues.  Phys.-Chem.  Soc.  4S,  835  (1911)  ;  Chem.  Alts.  6, 
478   (1912). 

«5Auwers,  Ann.  S73,  274  (1910). 


556       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

EXALTATION  OF  MOLECULAR  REFRACTION  CAUSED  BY  CONJUGATION  OF  Two 
ETHYLENE  LINKINGS. 

MD  EMD 

Substance  Calc.  Obs.  Reference 

A^-dicyclohexene,  C12H16/=2  52.34  52.65  0.31  66 

A'.8<9)-p-menthadiene,  C10H16,/=2 45.24  46.0  0.76  67 

Aa-8(9>-m-menthadiene,  C10H10/=a  45.24  46.6  1.36  67 

AW)-m-menthadiene,    CioHie,/— 2 45.24  46.3  1.06  67 

AVOO-O-menthadiene,   CioHift/— 2 45.24  46.0  0.76  68 

V>H  =  C          3   C10Hi6>/=2 45.24  45.69  0.45  69 

CH, 

/ <  ^CH2 

C          >—  CHa  —  C  CulW      ••••     49.86  50.13  0.27  69 

N W  \CH3 

CH, 

I 

/~     ^-CH^C  CuH18/=2..        49.86  50.39  0.54  69 

X r  \CH3 


iJW—  ....     49.86  49.97  0.11  69 

\CH3 

In  a  recent  paper  Auwers 70  carefully  reviews  the  effect  of  ring 
closing  on  the  molecular  refraction,  particularly  in  the  cyclohexane 
series  on  account  of  the  evidence  of  refractivity  as  to  the  constitution 
of  benzene.  Although  the  refractivities  of  the  saturated  cyclopen- 
tanes,  cyclohexanes  and  cycloheptanes  are  practically  normal,  it  is 
noted  that  the  expected  exaltation  of  the  molecular  refraction  nor- 
mally caused  by  conjugated  double  bonds  is  not  observed  in  the  case 
of  cyclopentadiene,  cyclohexadiene,  and  cycloheptadiene.  Still  greater 
differences  are  observed  between  the  cyclic  and  acyclic  conjugated 

••Wallach,   Goettingcn  Nachr.  October,   1910. 
87  Haworth,  Prekin  &  Wallach,  J.  Chcm.  Soc.  99,  123   (1911). 
"sperkin,  8th  Int.  Cong.  Appl.  Ghem.  VI,  244. 
89  Haworth  &  Fyfe,  J.  Ghem.  Soc.  105,  1662   (1914), 
^5,  98    (1918), 


PHYSICAL  PROPERTIES  557 

trienes,  the  exaltation  being  particularly  great  for  the  acyclic  hydrocar- 
bons but  very  slight  in  the  case  of  the  cyclic  conjugated  trienes.  It  was 
this  fact  which  caused  so  much  doubt  and  controversy  over  the  con- 
stitution of  A1-3-cyclohexadiene.  The  chemical  evidence  leaves  no 
room  for  reasonable  doubt  regarding  the  constitution  of  this  hydro- 
carbon and  that  it  is  by  no  means  an  exception  will  be  seen  from  the 
following  table,  E  Ma  and  E  M^  being  the  difference  between  the 

observed  and  calculated  values  for  the  a  hydrogen  and  sodium  D  lines 
respectively. 


E  M  E  M 


CH2  CH3 

iJH_CH  =  i 


H  +1.81  +2.10 


CH  -      CH2 

-CH  =  C 


CH  — CHr=CH  —0.45  —  0.4772 


CH  —  CH3     CH3 
CH  —  CH  =  CH 


+  1.96  +  2.03 


CH  —  CH2—  CH2 

CH  —  CH  =  CH  +  0.02  +  0.05  73 

CH  —  CH3  CH3 

CH  —  CH  =  CH  —  CH2  .....  1.6274 

CH  —  CH2  -  CH, 

II  I 

CH  —  CH  =  CH  —  CH2  +  0.50  ..... 

The  introduction  of  alkyl  groups  causes  a  definite  exaltation  of  the 
molecular  refraction  as  compared  with  the  unsubstituted  hydro- 
carbon. 

The  differences  in  the  following  series  of  trienes  are  particularly 
noteworthy,  Auwers  representing  benzene  as  cyclohexatriene, 

71  Ber.  49,  833    (1916). 

"Auwers,  Ber.  45,  3077    (1912). 

»  Harries,  Ber.  J,5,  809  (1912)  ;  Willstatter  &  Hatt,  Ber.  45,  1647  (1912). 

74  J.  prakt.  CJi€m.  (2)  82,  74   (1910). 


558       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

1 D 


E  Ma  EM 


CH  =  CH2         CH2  75 

i.. 


CH CH  +2.90  

CH  =  CH CH76 

—  0.18  —0.18 


CH  =  CH2        CH  —  CH3 

.8- 


-  CH3  +  4.07  +  4.J 

CH  =  CH  —  C  —  CH376 
CH  =  CH  — C  — CH3  +0.20  +0.19 


M  E  M^ 

a  D 


CH  =  CH2         CH  —  C2H5 

CH  =  CH C CH377  +3.89°  +4.19 


+  0.05 


CH  =  CH  —  C  —  C2H5 

CH  =  CH  — C  — CH3  +0.06 


CH3         CH3 

\/ 

CH  =  C             CH 

-CH, 

CH  —  CH          C 

CH,,  77                    -1-  3.99 

4-4.29 

(allo-ocimene) 
CH3— CH  — CH3 

CH^C CH 

CH  =  CH C  —  CH3  78  +  0.30  +  0.31 

Just  as  a  ketone  or  aldehyde  group,  in  conjugated  position  with 
reference  to  a  cyclopropane  group,  produces  abnormally  high  refrac- 

"Auwers  &  Eisenlohr,  J.  prakt.  Chem.  (20)  84,  40  (1911). 
"Landolt  &  Jahn,  Z.  Physik.   Chem.  10,  303    (1892). 
"Enklaar,  Rec.  trav.  cMm.  36,  215   (1917). 
'•Landolt  &  Jahn,  Z.  physik.  Chem.  10,  303  (1892). 


PHYSICAL  PROPERTIES  559 

tivity,  a  similar  effect  is  produced  by  ketone  and  ethylene  groups  in 
conjugated  positions,  for  example, 

Ma        E  M         x> 

Observed  Calc. 
H 

Crotonaldehyde,  CH3CH  =  CH.C  21.29        20.24        1.05 

0 
CH3 

Mesityl  oxide  (CH3)2C  =  CH.C  30.13        29.39        0.74 

0 

Carvenone,  46.52        45.82        0.70 

Menthenone,  46.78        45.82        0.96 

Aliphatic  conjugated  dienes  usually  show  exaltation,  as  in  2.4- 
hexadiene  E  Ma  =  0.98  isoprene,  E  M-Q  =1.0379  and  hexatriene 

EMa=2.06. 

As  noted  above,  unsaturated  cyclic  hydrocarbons  containing  two  or 
more  alkyl  side  chains  and  conjugated  double  bonds  usually  show 
exaltation,  as  in  a-phellandrene  and  a-terpinene.80 

CH3  CH3 

calc.=a44.97  A"D 

obs.  =45.35  calc.  =  45.24 

obs.  =46.15 

)3HT  C3H7 

a-phellandrene  a-terpinene 

Opinions  differ  as  to  whether  a  study  of  refractivity  has  really 
contributed  much  to  the  elucidation  of  the  constitution  of  substances 
such  as  a-terpinene,  and  as  to  whether  or  not  the  evidence  of  such 
physical  constants  can  be  relied  upon.  Usually,  as  in  the  case  of 
the  terpinenes,  our  most  trustworthy  evidence  has  resulted  from 


Calculated  from  recent  data  of  Harries,  Per.  yt,  1999  (1914),  using 

!^!  0.6867  gives  MD     25.38  ;  calcul 
«°Auwers,  Ber.  42,  2404,  2424   (1909). 


an<l  a  0.6867  gives  MD     25.38  ;  calculated  24.35. 


560      CHEMISTRY  OF  THE  NON-BENZEN01D  HYDROCARBONS 

chemical  investigation.81  In  this  connection  it  should  be  noted  that 
certain  substances  in  which  considerable  exaltation  might  be  expected, 
show  only  the  normal  refractivity,  as,  for  example,  cyclooctatetrene 
discovered  by  Willstatter.82 


20°  /=4 

I  I  n  -    1.53460         calc.  C8H8/  35.07 

HC=:CH.CH=:CH  D  obs.  35.20 

This  hydrocarbon  has  all  the  chemical  properties  which  one  would 
expect  such  a  substance  to  have  and  yet  benzene,  having  quite  dif- 
ferent chemical  properties  also  shows  only  very  slight  exaltation,  M  _ 

observed  25.93,  calculated  for  C6H6/=3  26.25.  Wallach  has  urged 
caution  in  interpreting  refractivity  values  and  conclusions  thus  drawn 
are  of  doubtful  value  unless  supported  by  other  good  evidence  and 
assurance  that  the  substance  examined  is  of  the  highest  purity.  Thus, 
methyl  heptenone  on  condensation  yields  a  material  which  for  a  long 
time  was  considered,  from  its  analysis  and  refractivity  value,  to  be 
dihydroxylene.  This  has  been  shown,  however,  to  be  a  mixture  of 
xylene  and  tetrahydroxylene.83  Early  in  the  study  of  refractivity 
Bruhl  stated  that  the  refractive  index  showed  that  the  terpenes, 
C10H16,  in  orange  peel  oil,  lemon  oil  and  bergamot  were  identical  and 
that  the  chemical  evidence  was  merely  confirmatory  but  not  neces- 
sary to  prove  this  fact.  Wallach  8*  pointed  out  that  on  such  grounds 
Bruhl  should  have  claimed  the  identity  of  limonene  and  sylvestrene, 
since  their  physical  constants  are  practically  identical. 


Limonene,  CioHw        Sylvestrene, 
Boiling-point  ......  .  .....        175°-176°  174°-176° 

d20"  ....................  0.845  0.847 

nD  .....................  1.4746  1.477 

MD  ....................          45.23  45.08 

The  close  agreement  of  these  constants  is  to  be  expected  from  the 
constitution  of  these  hydrocarbons  q.  v. 

Wallach  85  has  called  attention  to  the  fact  that  hydrocarbons  hav- 
ing a  semicyclic  double  bond  show  abnormally  high  refractivity. 


81  Wallach,  Awn.  S50,  142   (1906)  ;  374,  224   (1910) 

**Ber.  44,  3423   (1911). 

81  Wallach,  Ann.  395,  76  (1913)  ;  396,  273  (1913). 

"Ann.  245t  191    (1888). 

**Ann.  345f  142    (1906)  ;  360,  34    (1908). 


PHYSICAL  PROPERTIES 


561 


MOLECULAR  REFRACTION 


Calculated 


31.83 


31.83 


36.43 


41.03 


Observed 


Observed 


CHCH 


32.12 


31.89 


32.26 


31.8 


36.82 


^CH2CH3 


36.52 


)>=C(CH3) 


)>CH(CH3)2 


41.56 
_CH2  —  CH2 


41.02 
CH2  —  CH2—  CH 


36.43 


CH2  —  CH2 
36.64 


CH3 


36.43 


Similarly  the  terpenes,  terpinolene,  sabinene,  d.l.fenchene,  p-terpinene 
and  (3-pinene  have  been  shown  by  chemical  investigation  to  have  semi- 
cyclic  double  bonds,  >C  =  CH2,  and  the  exaltations  of  their  specific 
refractions  due  to  this  group  vary  from  0.3  to  0.5.  Auwers  86  there- 
fore argues  that  camphene  must  have  the  constitution  proposed  by 
Wagner  since  the  exaltation  of  the  molecular  refraction  (MD)  of 
camphene  is  0.51. 


MD  44.02  :calc.  43.51 


camphene  (Wagner) 

"Ann.  387,  240   (1912). 


562      CHEMISTRY  OF  THE  NON-BENZEN01D  HYDROCARBONS 

Here  also,  however,  the  chemical  evidence  is  much  more  convincing 
that  camphene  has  the  structure  shown.87 

The  refractive  index  has  been  of  very  little  value  in  the  examina- 
tion of  commercial  hydrocarbon  oils.  Rittman  and  Egloff,88  give  the 
results  of  the  examination  of  corresponding  fractions  of  seventeen 
different  petroleums,  five  from  California,  four  from  Pennsylvania, 
five  from  Oklahoma,  two  from  Russia  and  one  from  Mexico.  As  one 
would  expect  from  what  is  known  of  the  different  types  of  hydro- 
carbons present  in  different  petroleums,  the  refractive  indices  varied 
within  wide  limits. 

Fraction  Refractive  Indices 

To     100°  1.375  to  1.423 

100°-150°  1.407  to  1.434 

150°-200°  1.425  to  1.448 

200°-250°  1.437  to  1.465 

250°-300°  1.449  to  1.493 

The  refractive  indices  were  found  to  vary  as  the  specific  gravities. 

The  refractive  index  is  usually  determined  in  the  examination  of 
essential  oils  but  the  so-called  "constants"  obtained  are  of  no  value 
as  evidence  of  adulteration  unless  supported  by  other  good  evidence.89 

It  is  well  known  that  the  refractive  index  of  a  substance  varies 
with  the  wave  length  of  the  light  employed,  light  of  short  wave  length 
giving  the  greater  refraction.  The  dispersion  or  difference  in  the 
refraction  of  two  different  wave  lengths,  for  example,  the  a  and  y 
hydrogen  lines,  may  be  measured  and  the  specific  and  molecular  dis- 
persivities  calculated.90  However  such  determinations  can  hardly  be 
carried  out  except  in  a  well  equipped  physical  laboratory  and  the 
results  show  little  more  than  the  refractivity  for  a  single  wave  length, 
for  example,  the  sodium  D  lines,  a  strong,  nearly  monochromatic  and 
satisfactory  light  available  in  any  laboratory. 

Magnetic  Rotation. 

When  a  beam  of  polarized  light  is  passed  through  a  transparent 
substance  placed  between  the  poles  of  an  electro-magnet,  so  that  the 
light  travels  in  a  direction  parallel  to  the  lines  of  the  magnetic  field, 

8TCf.  Haworth  &  King,  J.  Chem.  Soc.  105,  1342  (1914);  Buchner.  Ber.  L6,  759, 
2108  (1913)  ;  Lipp,  B&r.  1,1,  871  (1919)  ;  Komppa,  Ber.  47,  934  (1914). 

88«7.  Ind.  &  Eng.  Chem.  1,  759   (1915). 

89  Cf.  Gildemeister  &  Hoffmann,  Die  Aetherischen  Oele,  Ed.  II,  Vol.  I,  580   (1910). 

80  Cf.  Auwers  &  Eisenlohr,  J.  prakt.  Chem.  (2)  82,  70  (1910);  Darmois,  Compt. 
rend.  Ill,  952  (1920)  ;  Falk,  J.  Am.  Chem.  Soc.  31,  86,  806  (1909)  shows  that  disper- 
sion, M0  —  M  Oor  My— Mfl  is  not  affected  by  temperature. 


PHYSICAL  PROPERTIES  563 

the  plane  of  the  polarized  light  is  rotated.  The  original  discovery 
was  made  by  Faraday,  but  has  been  thoroughly  investigated  by  W.  H. 
Perkin,  who  has  shown  that  the  magnetic  rotatory  power  of  a  sub- 
stance depends  partly  upon  its  constitution.  Perkin  has  applied  the 
method  to  the  study  of  the  constitution  of  certain  hydrocarbons,  but 
it  has  never  been  widely  employed,  probably  on  account  of  the  fact 
that  the  apparatus  required  is  rather  costly  and  involved;  that,  as 
Faraday  showed,  the  amount  of  rotation  is  proportional  to  the  strength 
of  the  magnetic  field ;  that  a  "series  constant"  must  be  employed  which 
is  different  for  each  slight  difference  in  constitution,  e.  g.,  0.508  for 
normal  paraffines  and  0.631  for  iso  paraffines  and  unknown  for  most 
of  the  other  possible  isomeric  types;  that  the  "constant"  increment 
for  the  double  bond  varies  from  0.578  to  1.112  in  different  types  of 
substances;  that  the  effect  of  substitution  may  vary  with  each  suc- 
cessive substituent  as  when  substituting  halogens.  In  spite  of  the 
very  admirable  and  painstaking  work  of  Perkin,  which  is  of  the  great- 
est interest  from  a  physical  standpoint,  the  method  has  not  proved 
of  great  value  in  the  investigation  of  hydrocarbons  and  the  reader  is 
therefore  referred  to  Perkin's  original  papers,91  or  to  other  sources  92 
for  further  information  in  regard  to  it. 

Optical  Activity. 

The  majority  of  the  terpenes  occurring  in  nature  are  optically 
active.  The  degree  of  rotation  of  a  particular  terpene  may  vary 
practically  from  the  one  extreme  value  to  the  other,  or  from  extreme 
Isevo  to  dextro-rotatory  power.  Bacon 93  noticed  that  the  rotatory  power 
of  specimens  of  phellandrene  distilled  from  Manila  elemi,  collected 
from  separate  trees,  varied  from  —  60.6  to  +  126.0.  Turpentine, 
chiefly  ex-pinene,  varies  in  much  the  same  way,  though  within  smaller 
limits.  The  turpentine  from  American  long  leaf  pine,  Pinus  palustris, 
is  preponderatingly  dextro  rotatory,  that  from  the  Cuban  pine,  Pinus 
heterophylla,  is  usually  Ia3vo  rotatory,  and  French  turpentine,  from 
Pinus  pinaster  is  usually  highly  Ia3vo-rotatory.  In  most  cases,  a  par- 
ticular species  yields  one  or  more  terpenes  whose  optical  activity  is 
characterized  by  being  strongly  dextro  or  la?vo-rotatory.  Thus  the 
Aleppo  pine  94  of  southern  Europe  yields  a  highly  dextro  a-pinene, 

91  J.  Chem.  Soc.  69   (1896)  ;  81.  315    (1902)  ;  89,  849   (1906)  ;  91,  835,  851    (1907). 

92  Cohen,  Org.  chem.  Vol.  II,  44,  Ed.  II   (1919).     Smiles,  Relations  between  Chemi- 
cal Constitution  and  Physical  Properties,  1910. 

93  Philippine  J.  Sci,  4,  96   (1909). 
•*Vezes,  Bull.  Soc.  chim.  (4)   5,  931   (1909). 


564       CHEMISTRY  OF  THE  NON-BENZENOW  HYDROCARBONS 
[a\\    4~  48.4°,  and  a-pinene  of  extreme  Isevo  rotation,  [a]  ^  —  48.63°, 

has  been  found  in  the  essential  oil  of  one  of  the  species  of  eucalyptus.95 
Optically  inactive  pinene  is  much  rarer  but  is  found  in  American 
oil  of  peppermint,  coriander  and  some  lemon  oils.  In  the  case  of 
limonene  the  dextro  form  is  much  the  commoner  variety  and  although 
the  nature  of  racemic  substances  had  long  been  understood,  it  was 
not  until  the  discovery  of  1.  limonene  that  Wallach  was  able  to  show 
that  equal  portions  of  d .  and  1 .  limonene  yield  the  derivatives  charac- 
teristic of  "dipentene."  Thus  dipentene  tetrabromide,  melting-point 
120°,  is  the  racemic  form  of  the  d.  and  l.tetrabromides  melting  at 
104°-105°. 

That  heat  tends  to  racemize  optically  active  hydrocarbons  is  well 
known  but  in  most  cases  distillation  at  atmospheric  pressure,  of  the 
terpenes,  does  not  appreciably  affect  the  rotatory  power.  Bacon  has 
noted  that  in  the  case  of  a-phellandrene  exposure  to  direct  sunlight 
causes  comparatively  rapid  racemization. 

When  it  is  attempted  to  prepare  optically  active  hydrocarbons  by 
decomposing  optically  active  alcohols,  racemization  occurs  simultane- 
ously and  the  resulting  hydrocarbons  are  usually  inactive.  Perkin 
and  K.  Fisher  decomposed  terpineols  by  magnesium-methyl  iodide  in 
the  cold,  and  also  by  heating  with  anhydrous  oxalic  acid  but  the 
resulting  hydrocarbon  was  dipentene.96  However,  Perkin  succeeded 
in  preparing  the  isomeric  hydrocarbon,  A3  8(9)-p-menthadiene,  in 
highly  optically  active  form  by  resolving  one  of  the  intermediate 
products  into  its~d  and  /.  forms.  The  acid 

CH2CH 

MeCH</  ")C.C02H 

CH2CH2 

was  resolved  by  means  of  brucine  and  strychnine  to  the  d.  acid 
MD+  101.1°  and  I  acid  [a]  — 100.8°.  The  ester  of  the  Isevo 

acid  was  then  treated  with  magnesium-methyl  iodide  to  form  Z.-A3-p- 
menthenol(S)  with  the  rotation  [a]  —  67.3°.  When  the  correspond- 
ing d.  alcohol  was  treated  in  the  cold  with  magnesium-methyl  iodide 
the  hydrocarbon  was  obtained  and  with  the  high  rotation  +  98.2°. 

98  Smith,  cf.  Schimmel  &  Co.  Bericht,   1899,   I,   22. 
86  8th  Int.  Cong.  Appl.  Chem.  6,  232  (1912). 


PHYSICAL  PROPERTIES  565 

CH3 


C02H  A° 

(a)      ±101°  CH3        CH3 

E>  ±  67.3° 

The  isomeric  m.menthadiene  was  also  obtained  in  an  optically  ac- 
tive form  by  resolving  the  unsaturated  acid  CH3  by  means  of 


\/C02H 

/.menthylamine  and  subsequent  reactions  as  in  the  case  of  the  p.men- 
thadiene. 

The  optical  activity  of  petroleum,  or  more  accurately,  certain 
fractions  of  petroleum  distillates,  is  one  of  the  most  significant  facts 
bearing  on  the  theory  of  the  formation  of  petroleum  from  organic 
remains.  According  to  Engler,97  no  oils  which  have  been  carefully 
examined  are  entirely  without  optical  activity.  Most  petroleums  are 
dextro-rotatory  but  a  l«vo  oil  has  been  reported  from  Borneo. 
Tschugaeff 98  called  attention  to  the  optical  activity  of  a  vaseline  oil 
in  1904  and  also  stated  the  importance  of  this  fact  to  the  theory  of 
organic  origin.  Rakusin "  then  reported  dextro-rotatory  fractions 
from  American,  Baku  and  Grossny  oils.  In  1835  Biot  10°  had  observed 
dextro-rotation  in  a  "naphtha"  of  unknown  origin  but  later  observers 
all  had  regarded  petroleum  as  optically  inactive.  Since  1904,  how- 
ever, many  observers  have  confirmed  the  fact  that  certain  fractions 
of  petroleums  are  optically  active.  Crude  petroleum  cannot  be  meas- 
ured for  optical  activity  on  account  of  the  color  and  asphaltic  matter 
which  is  frequently  present. 

Cholesterol  yields  oily  decomposition  products  when  subjected  to 
destructive  distillation  101  and  wool  grease  yields  optically  active  oils 
on  decomposition,  which  led  Marcusson102  to  attribute  the  optical 
activity  of  these  oils  and  petroleum  oils  to  decomposition  products  of 

"  Ber.  47,  3358   (1914). 

**J.  Russ.  Phys.-Chem.  Soo.  36,  453   (1904)  ;  Chem.  Ztg.  190$,  505. 

MJ.  Russ.  Phys.-Chem.  Soc.  36,  456  (1904)  ;  Chem.  Ztg.  190$,  505. 

^Mem.  de  I'acad.  Sci.  13,  139   (1835). 

1MWindaus,  Ber.  37,  2027  (1904). 

102  Chem,  Ztg.  1906,  788, 


566       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

cholesterol.  Engler  and  his  students  have  shown  many  points  of  sim- 
ilarity in  the  oils  from  cholesterol  and  optically  active  petroleum  frac- 
tions. Thus  when  cholesterol  is  rapidly  distilled  the  resulting  oil  is 
slightly  Ia3vo-rotatory  and  when  this  ^.distillate  is  heated  for  several 
hours  the  rotatory  power  diminishes  and  finally  becomes  dextro  rota- 
tory; a  closely  parallel  behavior  is  shown  by  the  two  Isevo-rotatory 
Java  oils.103 

The  chemical  character  of  the  optically  active  substance  in  petro- 
leum has  not  been  definitely  shown.  The  naphthenic  acids  isolated 
from  Baku  oil  are  feebly  active,10*  but  oils  which  have  been  entirely 
freed  from  these  acids  show  practically  undiminished  optical  activity. 
Engler  and  his  students  have  concentrated  the  optically  active  sub- 
stance by  repeated  fractional  distillation  in  vacuo  until  the  most  active 
fraction  represented  only  3  per  cent  of  the  original  material  but  was 
unable  to  find  indications  of  the  presence  of  any  substance  other  than 
hydrocarbons.  Evidence  that  the  optical  activity  of  all  petroleums 
is  .derived  from  a  common  original  material,  perhaps  choleresterol, 
is  afforded  by  the  fact  that  the  fractions  of  greatest  degree  of  rotation, 
of  the  various  petroleums  examined,  have  approximately  the  same 
range  of  boiling-point,  as  is  shown  by  the  following  table,  which  also 
shows  the  magnitude  of  rotation  of  these  fractions  after  concentra- 
tion by  repeated  distillation. 

MAXIMUM  OPTICAL  ACTIVITY  OF  PETROLEUM  FRACTIONS.105 

P 

Petroleum  Source  Fraction  B.-P.  °C  mm.  Saccharimetcr0 

Hanover   235-275  12  +10.4 

Baku   230-278  12-13  +17.0 

Galicia  260-285  12  +22.8 

Roumania    250-270  12  +22.0 

Pechelbronn    265-281  12.5  +7.6 

Pennsylvania    255-297  14  +1.0 

Java  268-281  15.5  +4.1 

Optical  activity  has  not  been  observed  in  petroleum  fractions  boil- 
ing below  200°  at  atmospheric  pressure. 

Specific  Heat. 

In  1831  Neumann  discovered  that  in  a  series  of  compounds  of 
analogous  composition  the  specific  heat  varies  inversely  as  the  mo- 

103  See  cholest&rylene. 

'Bushong  &  Humphrey,  8th  Int.  Gong.  Appl.  Chem.  6,  57   (1912). 
105  Engler,  Das  Erdol,  Vol.  I,  202,  1913.     For  Isevo-rotatory  oil  see  Jones  &  Woot- 
ton,  J.  Chem.  Soc.  91,  1146   (1907). 


Hydrocarbon 

Molecular 
Weight 
86 

Specific  Heat 
05272 

No.  of  Atoms 
20 

C  H 

,  100 

05074 

23 

CsHis          

114 

05052 

26 

128 

05034 

29 

r*9  H! 

142 

05021 

32 

r*  H 

156 

05013 

35 

C^HM 

170 

0.4997 

38 

C       Ho 

184 

0.4986 

41 

C  4Hao 

196 

0.4973 

44 

C15H32    

,  210 

0.4966 

47 

224 

0.4957 

50 

PHYSICAL  PROPERTIES  567 

lecular  weight.  Mabery  106  determined  the  specific  heats  of  a  series 
of  light  fractions  of  Pennsylvania  petroleum  probably  consisting  of 
normal  paraffine  hydrocarbons.  The  uniform  decrease  in  specific 
heat  with  increasing  molecular  weight  suggests  a  constant  relation 
analogous  to  the  law  of  Neumann.  In  the  following  table  the  con- 
stant K  is  expressed  in  terms  of  the  specific  heat  multiplied  by  the 
molecular  weight  and  the  product  divided  by  the  number  of  atoms 
in  the  molecule, 

Molecular 

K. 

2.26 

2.21 

2.21 

222 

2.23 

2.23 

2.23 

2.24 

2.23 

2.24 

2.23 

Mabery  also  gives  the  latent  heat  of  vaporization  of  the  following 
hydrocarbons, 

Heat 

of  Vaporization 
Boiling-Point  in  Calories 

Hexane  68°  79.4 

Heptane    98°  74.0 

Octane  125°  71.1 

Cyclohexane   68°-  70°  87.3 

Dimethylcyclopentane    90°-  92°  81.0 

Methylcyclohexane    98°  75.7 

Dimethylcyclohexane    118°-119°  71.7 

From  an  industrial  point  of  view  data  on  the  specific  heats  and 
heat  of  vaporization  of  various  petroleum  fractions  are  of  value  in 
order  properly  to  design  stills  and  condensers.107  According  to  Trou- 
tons'  rule  the  molecular  heat  of  vaporization  divided  by  the  absolute 
boiling-point  equals  a  constant,  which  is  approximately  20.  Graefe  108 
points  out  that  this  relation  can  be  employed  to  calculate  the  mean 
heat  of  vaporization  of  petroleum  fractions  (which  distill  at  atmos- 

106  Am.  Chem.  J.  28,  66   (1902). 

107  In  the  early  days  of  the  American  petroleum   industry  m-.ich  of  the  apparatus 
employed  was  perfected  and  developed  purely  by  the  cut  and  try  method.     Karawajeff 
[J.   Soc.   Chem.   Ind.  32,  128    (1910)]    states   that  the   average   specific   heat   of  heavy 
petroleum  oils  at  100°C  is  about  0.48,  rising  as  a  linear  function  of  the  temperature 
to  about  0.60  at  400°C.     For  the  specific  heats  at  low  temperatures  see  Bushong  and 
Knight,  J.  Ind.  &  Eng.  Chem.  12,  1197    (1920). 

108 Petroleum  5,  569  (1909)  ;  Chem.  Abs.  4,  1362  (1910). 


568       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

pheric  pressure  without  decomposition).  Graefe  used  a  rather  ingen- 
ious method  for  determining  the  mean  molecular  weight,  i.  e.,  lowering 
of  the  freezing-point  of  stearic  acid.  His  results,  calculated  in  this 
manner,  are  as  follows: 

Heat  to 

Average  Average  Heat  of   Raise  to  Total 

Material                       Sp.Gr.     Mol.Wt.     B.-P.  Vaporize     B.-P.  Heat 

Light  crude  oil 0.883            1 13           216°  86.5  82  168.5 

Gas  oil 0.890            158           273°  69.2  107  176.2 

Paraffine  oil,  light 0.920            190            328°  63.3  130  193.3 

"     heavy  ...     0.933           230            346°  53.8  138  191.8 

Values,    for    petroleum    distillates,    determined    calorimetrically 
usually  fall  within  the  range  130  to  190  calories. 


Thermochemistry  of  the  Non-benzenoid  Hydrocarbons. 

There  is  little  question  but  that  organic  chemistry  is  too  largely 
a  compendium  of  methods  of  preparation,  and,  considering  the  meager 
equipment  of  many  laboratories  and  the  ease  with  which  most  organic 
reactions  may  be  carried  out,  it  was  perhaps  inevitable  that  this 
should  be  so.  Also  the  difficulties  in  the  way  of  understanding  the 
theory  or  mechanism  of  organic  reactions  are  manifold,  and  many 
factors  other  than  thermochemical  relations  play  very  important 
roles.  Heat  changes  in  organic  reactions  are  often  small  and  reac- 
tions frequently  take  place  with  the  formation  of  substances  which 
do  not  directly  lead  to  increased  entropy  of  the  system;  stereo  chemi- 
cal relations  play  an  important  part,  many  phases  of  which,  for  exam- 
ple the  Walden  inversion,  we  are  far  from  understanding.  The  modi- 
fication of  the  chemical  properties  of  a  given  atom  or  element  by  neigh- 
boring substituents  of  pronounced  chemical  character  is  a  factor  which 
we  know  mostly  in  a  qualitative  way,  in  much  the  same  way  that  a  chef 
is  familiar  with  the  strength  of  his  assortment  of  condiments.  We 
know  in  a  more  or  less  quantitative  way  that  a  condition  of  stress  in 
a  molecule  affects  certain  physical  properties  and  endows  the  sub- 
stance with  unusual  chemical  activity,  as  for  example  cyclopropane. 
Thermochemical  data  have,  as  yet,  been  of  very  little  assistance  to 
organic  chemists.  Thus,  according  to  Thomsen,  ethylene  oxide  must 
have  the  structure  H2C.O.CH2  "for  the  introduction  of  an  atom  of  oxy- 
gen into  the  molecule  of  ethylene,  in  place  of  the  double  linkage,  corre- 
sponds to  a  thermal  effect  of  93.98-73.47  =  20.51  Calories,  since  the 


PHYSICAL  PROPERTIES  569 

taking  up  of  an  atom  of  oxygen  by  the  ethane  molecule  in  place  of  the 
single  linkage  produces  a  heat  effect  of  124.95-104.51  =  20.44  Calories. 
The  relation  is,  therefore,  exactly  the  same,  and,  if  dimethyl  ether  has 
the  composition  CH3.O.CH3  ethylene  oxide  must  be  dimethylene  ether, 
CH2.O.CH2.  The  view  that  ethylene  oxide  contained  a  single  link- 
age between  the  carbon  atoms  (CH2 —  CH2)  would  necessitate  a  heat 

\' 

of  formation  greater  by  14.71  Calories,  that  is  to  say  about  15  per 
cent  higher  than  the  experimental  value." 109  No  organic  chemist 
would  accept  Thomsen's  proposed  structure  of  this  substance  in  view 
of  its  many  chemical  reactions  which  point  clearly  to  the  ethylene 
oxide  formula.  Early  in  the  use  of  the  refractometer,  Wallach  cau- 
tioned Briihl  that  the  refractive  index  should  not  be  relied  upon  to 
decide  questions  of  constitution  unless  well  supported  by  chemical 
evidence  and  the  history  of  such  disputed  cases  has  amply  borne  out 
Wallach 's  contention.  Thus  in  the  case  of  thermochemical  evidence 
as  to  the  constitution  of  benzene  and  other  organic  compounds,  it 
should  always  be  kept  in  mind  that  in  the  present  state  of  our  knowl- 
edge thermochemical  data  are  evidence,  not  necessarily  proof. 

Also  in  many  organic  systems  the  mere  number  of  reactions 
which  are  observed  to  take  place  precludes  quantitative  predic- 
tion, at  least  in  the  light  of  our  present  understanding.  For  example, 
in  the  pyrolysis  of  the  simpler  paraffine  hydrocarbons  we  can  calcu- 
late the  thermal  changes  involved  in  a  large  number  of  reactions,  some 
exothermic  and  others  endothermic.  One  author  has  been  criticised 
for  employing  the  Nernst  formula  to  calculate  the  reaction  velocities 
of  a  large  number  of  possible  and  impossible  reactions  of  hydrocar- 
bons at  various  temperatures,  for  example, 

K  K  K 

600°  750°              900° 

C  +  H2  >  CH4                                 0.077  0.012  0.003 

C2H6 »C2H4  +  H2                          0.0027  0.094  1.28 

Experimentally  it  has  been  shown  that  ethylene  is  produced  to  a  less 
and  less  extent  as  the  temperature  rises  within  this  range,  the  per- 
centage of  ethylene  after  one  minute  being,  at  675°,  24  per  cent;  at 
810°,  11  per  cent;  at  1000°,  7  per  cent.110 

109  Thomsen-Burke,  Thermochemistry,  1908,  453. 

110 Bone  &  Coward,  J.  Chem.  Soc.  93,  1197   (1908). 


570       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

As  pointed  out  by  Thomsen,  the  determination  of  the  thermal! 
effect  which  should  result  on  formation  of  organic  substances  from  their] 
elements  is  particularly  difficult,  for  only  a  few  such  substances  can! 
be  so  formed  and  these  only  under  conditions  which  practically  pre-1 
elude  such  measurement.  No  satisfactory  method  is  at  present  known  1 
for  the  measurement  of  these  values,  except  determination  of  the] 
heats  of  combustion.  The  heats  of  combustion  of  a  number  of  hydro-] 
carbons,  as  found  by  Thomsen,  are  given  in  the  table  below. 

"The  third  column  gives  the  heats  of  combustion,  which  in  the! 
case  of  non-gaseous  bodies  is  given  in  the  state  of  gas  or  vapor  at  18°.  i 
In  each  case  it  is  assumed  that  the  products  of  combustion  are  cooled 
to  18°,  and  that  consequently  carbon  dioxide  and  nitrogen  appear  as 
gases, — water,  on  the  other  hand,  as  a  liquid." 

"The  fourth  column  gives  the  heats  of  formation  of  the  products  of 
the  combustion;  that  is  to  say,  the  amount  of  heat  which. is  evolved  by 
the  elements  of  the  compound  when  they  are  burned  in  the  free  state, 
as,  for  instance,  carbon  to  the  dioxide,  and  hydrogen  to  water.  The 
heat  of  combustion  of  carbon  is  taken  as  96,960  c.  for  each  gram-atom 
of  carbon,  this  being  the  heat  of  combustion  of  amorphous  carbon. 
The  heat  of  formation  of  water  is  68,360  c.  per  gram-molecule." 

"The  fifth  and  sixth  columns  contain  the  heats  of  formation  of 
th£  substances  in  the  state  of  gas  or  vapor  at  18°.  This  value  is  cal- 
culated from  the  heats  of  combustion  according  to  the  equation 
already  given. 

(Ca,  H2b,  0.)  -  -»  a(C,0,)  +  b(H,,0)— f(C.H,b,0.) 

"The  values  calculated  in  this  manner  are  the  heats  at  formation  at 
constant  pressure.  External  conditions,  however,  exercise  a  certain 
influence  on  these  values,  since  the  products  formed  usually  occupy 
a  smaller  volume  than  the  sum  of  the  volumes  of  the  constituent  ele- 
ments. Thus  2  gram-molecules  of  hydrogen  are  required  for  the 
formation  of  1  gram-molecule  of  CH4;  this  corresponds,  therefore,  to 
a  decrease  in  volume  of  1  gram-molecule  of  hydrogen,  or  of  22,340 
cubic  centimeters,  at  0°  and  760  mm.  pressure.  Such  a  diminution  of 
volume  will  result  in  the  evolution  of  543  c.  at  0°,  which  corresponds 
to  580  c.  at  18°.  If  now  from  the  heat  of  formation  of  the  compound 
we  subtract  580  c.  for  each  gram-molecular  volume  which  has  dis- 
appeared, we  obtain  the  heat  of  formation  at  constant  volume.  It  is 
this  value,  which  is  given  in  the  sixth  column  of  the  following  tables: 


PHYSICAL  PROPERTIES 
HYDROCARBONS. 


571 


(2a  +  b)OaC02  +  bH2O 

Heat         Heat      Heat  of  Formation 

of  Com-     of  For-  of  the  Compound 

Combustion :  CaH2b        bustion     motion  at  Con-  at  Con- 
Molecular                         of  the        of  the  stant  slant 
Compound                Formula                    gas  at  18°   products  pressure  volume 

PARAFFINS. 

Methane    CH4    211,930c.    233,680c.  21,750c.  21,170c. 

Ethane C2H«    370,440      399,000  28,560  27,400 

Propane C3Hs    529,210       564,320  35,110  33,370 

Trimethylmethane  ....  CH(CH3)3    687,190       729,640  42,450  40,130 

Tetramethylmethane. .    C(CH3)4     847,110       894,960  47,850  44,950 

Diisopropyl    (CH)2.(CH3)4    ....  999,200    1,060,280  61,080  57,600 

UN  SATURATED  HYDROCARBON  S . 


Ethylene    

C2H4    

333,350 

330,640    —  2,710    —  3  290 

Propylene,  normal   .  .  . 
Trimethylene    

CH.rCH.CH.    .... 

492,740 
499,430 

495,960    +3,220    +2,060 
495,960    —  3,470    —  4  630 

Isobutylene  
Isoamylene    

CH2:C:(CH3)2    ... 

650,620 
807630 

661,280  +10,660    +8,920 
826  600  +  18  970  +  16  650 

Diallyl   

C  H   C  H- 

932  820 

923  560    —  9  260  —  1  1  580 

Acetylene    

Allylene 

CH'CH  . 
CH'C  CH3 

310,050 
467550 

262,280  —47,770  —47,770 
427600  —39950  —40530 

Dipropargyl   . 

882,880 

786,840  —96,040  —97,200 

According  to  Thomsen  isomeric  organic  substances  may  give  iden- 
tical heats  of  combustion,  for  example, 

Allyl  chloride,  CH2  =  CH.CH2C1  454.68  Cal. 

2-Chloropropylene  CH2  =  CHC1 .  CH3  453.37  Cal. 

and  the  two  isomeric  dichloroethanes, 

Ethylene  chloride  CH0C1.CH,C1  296.36  Cal. 

Ethylidene  chloride  CH3CH.C12  296.41  Cal. 

It  should  be  pointed  out  that  the  chemical  properties  of  these  isomers 
differ  widely,  for  example,  the  chlorine  atom  is  much  more  stable  or 
firmly  bound  in  2-chloropropylene  than  in  allyl  chloride,  and  ethyli- 
dene  chloride  is  much  more  reactive  to  water  and  alkalies  than 
ethylene  chloride.  However,  T.  W.  Richards ni  has  developed  ex- 
ceedingly accurate  methods  of  calorimetry  by  which  he  has  detected 
slight  differences  in  the  heats  of  combustion  of  five  isomeric  octanes, 
and  it  is,  therefore,  possible  that  Thomsen's  conclusions  regarding  the 
identity  of  the  heats  of  combustion  of  isomers  such  as  the  above  may 
have  to  be  modified.  The  differences  in  the  heats  of  combustion  for 
the  octanes  studied  by  Richards  are  considerably  greater  than  the 
experimental  error  of  his  method  of  measurement.  The  values  found 
by  him  are  as  follows, 

111  Richards  &  Jesse,  J.  Am.  Ghent.  Soc.  32,  268  (1910)  ;  S6,  248  (1914). 


572       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

Normal  octane,  liquid  5448  Kilojoules 

2,  5  dimethylhexane   5442 

2  methylheptane   5454 

3.4  dimethylhexane 5444 

3  ethylhexane  5439 

Richards  and  Davis  112  find  that  the  increase  in  the  heat  of  combus- 
tion by  substituting  CH3  for  a  hydrogen  atom  in  a  side  chain  is 
648  ±  4  kilojoules,  but  when  substituted  for  a  hydrogen  of  the  ben- 
zene nucleus  the  value  is  638  kilojoules. 

It  is  greatly  to  be  regretted  that  so  few  thermal  measurements  of 
organic  substances  have  been  determined  with  the  accuracy  of  Rich- 
ards' measurements.  It  would  be  of  interest  to  determine  if  the  high 
degree  of  molecular  symmetry  of  tetramethyl  methane  C(CH3)4  and 
2,2,3,3,tetramethylbutane 

CH3         CH3 

CH3C-        -CCH3 
CH3         CH3 

which  are  characterized  by  abnormally  high  melting-points,  show 
heats  of  combustion  appreciably  different  from  their  normal  isomers. 
The  effect  of  conjugation  of  double  bonds  upon  the  l^at  of  com- 
bustion has  been  carefully  investigated  by  Auwers,  Roth  and  Eisen- 
lohr.113  A  number  of  terpenes  were  used  in  the  investigation  and. 
since  empirical  expressions  for  the  determination  of  the  "calculated 
values"  of  heats  of  combustion  are  not  trustworthy,  the  average  of  the 
experimental  values  determined  for  limonene,  i-limonene  and  sylves- 
trene,  1464  Calories  was  taken  as  a  normal  value  for  this  terpene 
series.  The  values  found  for  the  molecular  heats  of  combustion  were 
as  follows, 

Calories 

d.-limonene  [A^W-p-menthadiene]    1466 

i-limonene    1462 

sylvestrene  [A1-8<9)-m-menthadiene] 1464 

a-phellandrene   1434 

a-terpinene    1428 

d-a-pinene    1469 

camphene  (liquid)    1471 

sabinene    1475 

According  to  their  results  hydrocarbons  having  two  conjugated  double 
linkings  have  molecular  heats  of  combustion  about  two  per  cent  lower 
than  the  isomeric  hydrocarbons  containing  two  non- conjugated  double 

112  J.  Am.  Chem.  Soc.  W,  1599   (1920). 
118  Ann.  373,  267    (1910)! 


PHYSICAL  PROPERTIES  573 

linkings.  These  "thermal  depressions"  are  about  of  the  same  order 
of  magnitude  as  the  exaltations  of  molecular  refractivity  of  such 
hydrocarbons.  On  account  of  the  refined  experimental  technique  re- 
quired to  make  such  thermal  measurements  with  great  accuracy,  the 
thermal  method  will  never  displace  the  optical  methods  but  may  be 
helpful  as  an  auxiliary  in  certain  cases.  Thermal  measurements  made 
in  the  course  of  this  work  support  the  contention  that  Semmler's  car- 
venene  is  identical  with  a-terpinene.  The  parallelism  between  the 
thermal  and  optical  data  disappears  in  the  case  of  the  bicyclic  ter- 
penes.  The  heats  of  combustion  of  a  number  of  cyclic  hydrocarbons 
have  been  reported  by  Zuboff,114  as  follows,  expressed  as  Calories  per 
gram  molecule,  based  on  Regnault's  determination  of  the  specific  heat 
of  water, 

Hydrocarbon  Heat  of  Combustion 

Formula                     Name                                At  Const.  Vol.        At  Const.  Pres. 

Normal  Hexane   997.8                        999.8 

Methylcyclopentane     945.7                        947.4 

Cyclohexane    943.4                        945.1 

1.3  Dimethylcyclopentane 1099.5  1101.5 

Methylcyclohexane     1100.8  1102.8 

"      '  Cycloheptane    1096.3  1098.3 

C8H16    1.1   Dimethylcyclohexane    1252.8  1255.1 

1.3  "               "              1248.1  1250.4 

1.4  "                "         1238.9  1241.2 

C9H18    1.3.3   Trimethylcyclohexane    1406.0  1408.6 

CTHi2    Methylcyclohexene,  a   ..' 1047.6  1049.3 

/3  1053.2  1054.9 

Cycloheptane    1058.7  1060.5 

Roth  and  Auwers  115  have  criticised  the  technique  of  Stohmann's 
earlier  work  and  point  out  that  many  of  the  hydrocarbons  investi- 
gated by  Stohmann  very  probably  were  impure.  They  have  redeter- 
mined  the  heats  of  combustion  of  a  series  of  benzene  and  cyclohexane 
derivatives  which  were  most  carefully  purified.  Their  results  differ 
somewhat  from  Stohmann's  and  their  results  show  that  the  increase  in 
the  heat  of  combustion  produced  by  the  addition  of  two  hydrogen 
atoms  to  the  aromatic  hydrocarbon  is  much  greater  than  that  due  to 
the  addition  of  hydrogen  to  the  dihydro  and  tetrahydro  compounds; 
the  latter  two  increases  also  are  not  the  same.  The  difference  between 
the  heats  of  combustion  of  a  conjugated  cyclohexadiene  and  the  cor- 
responding aromatic  hydrocarbon  is  about  64  Calories.  The  difference 
between  that  of  a  conjugated  cyclohexadiene  and  the  cyclohexene  is 
about  50  Calories,  and  the  difference  between  the  cyclohexene  and  the 

114  J.  Russ.  Phys.-Chem.  Soc.  33,  708   (1901). 
118  Ann.  407,  145   (1915). 


574       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

cyclohexane  is  about  45  Calories.  In  the  case  of  simple  acyclic  ole- 
fines  the  difference  between  the  saturated  and  unsaturated  substance 
is  about  37  Calories  and  Roth  and  Auwers  state  that  hydrogenation 
appears  always  to  be  an  exothermic  reaction.  The  following  values 
(Calories)  are  the  molecular  heats  of  combustion  at  constant  pressure 
and  at  the  specified  initial  temperature. 

Substance  Calories  Temp. 

benzene    782.3  20.4° 

cyclohexene    893.7  21.0° 

cyclohexane    938.5  17.4° 

toluene   935.2  19.0° 

1-methylcyclohexene    1049.6  15.7° 

ra-xylene 1089.5  20.6° 

1.4-dimethyl-A1>3-cyclohexadiene    1153.7  19.5° 

1-ethylcyclohexene 1205.4  14.9° 

l-methyl-4-ethyl-All3-cyclohexadiene    1312.5  20.0° 

l-methyl-4-isopropyl-A1-3-cyclohexadiene    1472.2  20.5° 

naphthalene  (solid)    1235.2  

(liquid)    1239.7 

A'-dihydronaphthalene    1297.8  20.5° 

A8-  "  (solid)    1299.8  20.7° 

(liquid)     1302.7 

1.2.3.4.  tetrahydronaphthalene     1341 .2  20.0° 

decahydronaphthalene    1503.9  19.2° 

The  heat  energy  represented  by  the  single  bond  carbon  to  carbon 

\      / 

—  C  —  C  —  may  be  ascertained  by  reference  to  the  heats  of  combus- 

/      \ 

tion  of  the  paraffine  series  and  the  intramolecular  energy  of  H2,  the 
hydrogen  molecule.  Richards  and  Jesse 116  showed,  in  a  series  of 
unusually  accurate  determinations  on  very  carefully  purified  octanes, 
that  the  mean  value  for  the  octanes,  C8H18  is  1299.9  Calories. 

The  average  value  for  CH2  is  156  Calories.  The  heat  of  combustion 
of  carbon  and  of  hydrogen  in  hydrocarbons  of  the  paraffine  series  may 
be  determined  by  the  simultaneous  equations  shown  below,  using  the 
heats  of  combustion  of  ethane  and  propane  found  by  Berthelot  and 
Matignon,117  X  being  the  heat  of  combustion  of  a  carbon  atom  and  Y 
the  heat  of  combustion  of  a  hydrogen  atom, 

C2H6,    2X  +  6Y  =  370.9  Calories 

C3H8     3X  +  8Y  =  526.7 

From  these  equations  X  =  96.5  Calories  and  Y  =  29.65  Calories: 
also  if  we  take  X  +  2Y  =  156  together  with  the  mean  octane  value 
1299.9  Calories,  then,  in  round  figures,  X  =  96  and  Y  =  30  Calories. 

116  J.  Am.  Chem.  Hoc.  1910,  292. 

117  Ann.  chim.  phys.    (0)   30,  547    (1893). 


PHYSICAL  PROPERTIES  575 

Since  this  value  is  an  additive  one,  it  follows  that  the  energy  of  dis- 
sociation of  C-H  and  C-C  bonds  are  practically  equal,  or  within  the 
limits  of  experimental  error;  for  example,  if  there  were  a  noticeable 
difference  between  the  heat  of  dissociation,  or  rupture,  of  C-H  and 
C-C,  then  the  factor  would  be  very  different  for  C2H6,  having  6  C-H 
bonds  and  one  C-C  bond,  than  with  C8H18,  having  18  C-H  bonds  and 
seven  C-C  bonds. 

As  noted  above  hydrogen  in  the  parafBne  hydrocarbons  has  a  heat 
of  combustion  of  30  Calories;  by  burning  hydrogen  gas,  however,  the 
molecular  heat  of  combustion  is  not  2x30  or  60  Calories  but  67.5 
Calories.  This  difference,  7.5  Calories,  can  be  due  only  to  the  greater 
intramolecular  energy  of  the  hydrogen  molecule.  Langmuir 118  and 
Isnardi 119  have  calculated  the  heat  of  dissociation  of  hydrogen  from 
other  observations  and  both  agree  on  the  value  90  Calories  for  higher 
temperatures  and  Nernst120  has  calculated  that  at  absolute  zero  the 
value  would  be  about  100  Calories.  Using  Nernst's  value  the  heat  of 
dissociation  of  the  carbon-hydrogen  bond,  and  also  the  carbon-carbon 
single  bond,  is 

100  —  7.5  =  92.5  Calories.121 

A  second  carbon-to-carbon  bond  as  in  ethylene,  H2C  =  CH2.  has 
a  much  smaller  heat  of  dissociation.  Thus  for  ethylene: 

Calculated,  C2H6,  2  x  96  +  4  x  30  =  312  Calories 
Found  by  Berthelot122  340        " 

Found  by  Mixter 123  344.6     " 

The  increase  for  the  double  bond  is,  according  to  these  observa- 
tions, 28  to  32.6  Calories,  and  the  differences  between  the  observed 
values  and  those  calculated  in  the  same  manner  in  the  case  of  other 
olefines,  agree  very  well  with  the  above  values,  for  example, 

Propylene,  calculated    468.0  Cal. 

Propylene,  found    (Berthelot)    497.9  Cal. 


Difference    29.9  Cal. 

Hexylene,  calculated 936.0  Cal. 

Hexylene,124  liquid,  959.9  Cal.,  and  adding 

7.8  Cal.  for  heat  of  vaporization 967.7  Cal. 


Difference    31.7  Cal. 

118  Z.  Elektrochem.  23,  242   (1917). 

119  Z.  Elektrochem.  21,  416   (1915). 

320  Die  Grundlagen  des  neuen  Warmesatzes,  1918,  153. 

121  Weinberg,  £er.  52,  1501   (1919). 

122  Ann.  chim.  phj/s.    (6)   30,  557    (1893). 
323  Cliem.  Zentr.  1901  (2),  1250. 

1=1Zubow,  cf.  Landolt  &  Bornstein,  Physikalische  Tabellen,  Ed.  1912,  909. 


576       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

The  mean  value  for  the  increase  in  the  molecular  heat  of  com-? 
bustion  of  simple  olefines  is  therefore  about  30  Calories  greater  thai! 
the  value  calculated  from  the  number  of  carbon  and  hydrogen  atoma^ 
contained  in  the  hydrocarbon.  In  the  case  of  conjugated  diolefines, 
however,  the  difference  between  the  observed  and  calculated  values  is 
not  2  x  30  =  Calories,  but  a  very  much  smaller  value,  for  example, 

A2"4-Hexadiene 

Calculated  (6  x  96  +  10  x  30)    876.0  Cal. 

Observed 125  884.7  +  7.6 892.3  Cal. 


Difference    16.3  Cal. 

Other  differences  of  the  same  order,  between  the  observed  and  calcu- 
lated values  for  the  dienes,  have  been  observed.126 

Dielectric  Constants:  The  electrical  insulating  value  of  the  paraf* 
fines,  and  refined  mineral  oils  generally,  is  taken  advantage  of  in 
the  utilization  of  oils  for  transformers,  and  the  use  of  paraffine  in  im- 
pregnating the  cotton  insulation  of  wires  carrying  low  voltage  cur- 
rents. The  dielectric  constant  of  paraffine  wax  has  been  referred  to 
Under  this  head.  This  very  property  which  makes  these  hydrocarbon 
oils  valuable  as  insulating  material  is  a  source  of  considerable  danger 
in  the  case  of  the  more  volatile  mineral  oils  of  low  flash  point  since 
they  easily  become  electrostatically  charged  by  friction,  as  by  being 
pumped  through  a  pipe,  or  agitating  woolen  goods  in  a  gasoline  clean- 
ing mixture.  Electrical  spark  discharges  caused  in  this  way  have  re- 
sulted in  many  disastrous  explosions  and  fires.  Holde 12T  states  that 
light  petroleum  oils  can  easily  acquire  a  charge  amounting  to  several 
thousand  volts  by  being  pumped  through  a  metal  pipe.  Even  when  the 
pipes  and  containers  are  grounded  it  is  possible  that,  in  the  case  of  such 
good  insulators,  the  electrical  charge  cannot  be  sufficiently  rapidly  dis- 
sipated. Holde  gives  the  specific  conductivity  of  "light  petroleum" 
as  10"14  to  10'15.  Decrease  of  the  dielectric  constant  with  rise  in  tem- 
perature is  very  small,  the  temperature  coefficient  for  cyclohexane 
being  0.00078. 

Viscosity. 

Measurements  of  viscosity  have  been  of  value  as  evidence  of 
molecular  association,  the  formation  of  hydrates  in  aqueous  solution, 
the  existence  of  racemic  liquid  substances  and  Dunstan  and 

125  Roth  &  Moosbrugger,  Ann.  ^07,  153    (1915). 

28  The  effect  of  conjugation  of  double  bonds  on  the  heat  of  combination  is  of  par- 
ticular interest  in  connection  with  the  constitution  of  benzene.  Cf.  Weinberg,  Her. 
o&j  loul  (1019^. 

m  Ber.  JfH,  3239   (1914). 


PHYSICAL  PROPERTIES  577 

Thole  128  have  noted  certain  facts  which  indicate  that  this  property  is 
to  a  certain  extent  influenced  by  the  constitution,  of  organic  substances. 
From  the  few  facts  which  are  known,  it  appears  that  the  normal  paraf- 
fines  pentane,  hexane,  heptane  and  octane,  have  slightly  greater  viscos- 
ities than  their  branched  chain  isomers.129  Ortho-xylene  has  a  greater 
viscosity  than  meta  or  para-xylene,  but  the  viscosities  of  a  number 
of  isomeric  non-benzenoid  hydrocarbons  have  never  been  compared. 
Alicyclic  hydrocarbons  have  greater  viscosities  than  paraffines  of  the 
same  boiling-point  but  as  to  the  constitution  of  mineral  lubricating 
oils  practically  nothing  is  known. 

Viscosity  decreases  rapidly  with  rise  in  temperature  and  the  curves 
are  apparently  hyperbolic.180 

The  relation  between  viscosity  and  lubrication  has  been  reviewed 
by  Mabery  and  Mathews,131  who  point  out  that  while  viscosity  is 
generally  accepted  as  a  standard  of  value  in  classifying  lubricating 
oils,  it  is  not  certain  that  it  is  reliable  as  indicating  the  durability  and 
wearing  qualities  of  oils  differing  widely  in  composition.  The  vis- 
cosity of  lubricating  oils  has  received  considerable  attention  from 
engineers  and  analysts  and  many  forms  of  apparatus  have  been  pro- 
posed for  its  determination,  but  these  instruments  all  give  arbitrary 
values,  which  are  the  resultants  of  several  factors,  of  which  viscosity 
is  one.  Most  of  these  instruments  measure  the  rate  of  flow  of  the 
oil  through  an  orifice  and  the  interpretation  of  the  results  is  based 
upon  the  assumption  that  the  flow  of  oil  through  an  orifice  is  a  cor- 
rect measure  of  surface  viscosity  between  bearing  surfaces.  Mabery 
and  Mathews  obtained  a  set  of  relative  values  for  the  specific  viscosity 
of  hydrocarbons  obtained  by  fractional  distillation  of  petroleum. 
They  employed  Ostwald's  method  in  which  the  oil  is  made  to  flow 
through  a  capillary  tube  under  a  definite  pressure.  The  various  frac- 
tions had  approximately  the  composition  indicated  by  the  formulae. 

Spec.  Viscosity 
Hydrocarbon  Boiling-Point  Sp.  Gr.  at  20° 

CTHM  98°-100°  0.724  0.51 

C8HM   125°  0.735  0.60 

doHa    172°-173°  0.747  0.96 

CisH*, 212°-214°  0.769  149 

Ci5H«   158°-159°(50mm.)  0.793  2.79 

CicH^    174°-175°       "  0.799  335 

CwH*. 199°-200°       "  0.813  5.97 

128Cauwood  &  Turner,  J.  Chem.  Soc.  ion,  276  (1915). 
128  Thorpe  &  Roger,  Phil.  Trans.  185A,  397   (1894)  ;  189A,  71   (1897). 
uo  Bingham   &    Harrison,   Z.   physik.    Chem.    66,    1    (1909).     Dunstan   and    Stevens 
have  determined  the  viscosities  of  a  number  of  typical  lubricating  oils  at  temperatures 
within  the  range  70°-200°C  and  plotted  the  results  in  curves.     J.  Soc.  Chem.  Ind.  30. 
1063  (1921). 

lilJ.  Am.  Chem.  Soc.  SO,  992  (1908). 


578       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

That  the  paraffines  have  markedly  lower  viscosities  than  the  cyclic 
hydrocarbons  of  the  same  boiling-point  is  shown  by  the  following, 
determined  at  60°. 

Series                                Boiling-Point  Sp.  Gr.  Spec.  Viscosity 

CnH2n+2  .........  274°-276°  (50mm.)  0.775                8.51 

CnH2n-2  .............  274°-276°       "  0.835               15.63 

CnHan+2  .............  294°-296°       "  0.781                10.88 

CmH2n-2  .............  294°-296°       "  0.841               21.23 

The  marked  effect  of  ring  closing  and  the  very  slight  effect  of  un- 
saturation  is  also  shown  by  the  following  comparative  values  found 
by  Thole.182 


Substance  v\25°  -2  x  101 

Hexane                            CH2  —  CH2  —  CHa  .  .  0.00311  4.2 

Cyclohexane                                             :  0.00894  12.6 
CH2  —  CH*  —  CH3 

Methylbutyl  ketone       CH2  —  CHa  —  CO  ............      0.00584  5.8 

Cyclohexanone                  |                        |  0.0280  29.1 
Cxii2  —~  C^xia  .  .  OHj 


Methylamyl  ketone       CH2  —  CH2  —  CHa  —  CO 0.00766  5.9 

.CHa 


Cycloheptanone  0.0259  20.6 

CH2-<— 


Hexane    .............................................  0.00311  4.2 

Diallyl  CH2  =  CH  .  CH2  CH.CH  =  CH2  ..............  0.00269  4.0 

Isopentane  m  (CH3)2CH.CH2CH3  .....................  0.00223  4.3 

Trimethylethylene  (CHa)2C  =  CH.CHs  ..............  0.00212  4.3 

Isoprene  CH2  =  C(CH3)  .CH  =  CH2   .................  0.00214  4.6 


Removal  of  paraffine  wax  improves  the  viscosity  of  lubricating  oils, 
as  is  shown  by  the  following  data  of  Mabery  and  Mathews. 

INFLUENCE  OF  SOLID  PARAFFINE  ON  VISCOSITY  AT  20°. 

Boiling-Point  Specific 

Hydrocarbon  (60mm.)  Sp.  Gr.         Viscosity 

(a)  Penn.  distillate    CnHan-a     cooled  to 

—  10°  and  filtered  ...............     312°-314°  0.868  88.16 

(a)  +2.5%  solid  paraffine  of  same  boil- 

ing-point   ........................     312°-314°  0.868  82.30 

(b)  Penn.  distillate    CnH2n_2     cooled  to 

—  10°  and  filtered  ................     276°-278°  0.861  37.57 

(b)  -f-  2.5%  solid  paraffine  of  same  boil- 

ing-point .........................    276°-278°  0.860  36.39 

It  is  generally  recognized  that  the  real  function  of  oil  in  lubrication 
is  to  maintain  a  liquid  film  between  the  moving  metal  surfaces.13* 
Under  pressure  the  tendency  is  for  the  oil  to  be  squeezed  out  and  the 

»2J.  CJiem.  Soc.  105,  2004   (1914). 

»»  Thorpe  &  Rodger,  Phil.  Trans.  185A,  570   (1894). 

»««f.  Ubbelohde,  Petr.  Rev.  27,  293,  325   (1912). 


PHYSICAL  PROPERTIES  579 

oil  film  broken;  the  cohesion  of  the  oil  film  itself  and  its  tendency  to 
wet  or  adhere  to  the  metal  surface  and  its  ability  to  penetrate  inter- 
stices by  capillarity  are  factors  of  prime  importance.  While  these 
factors  may  not  be  generally  recognized,  viscosity  has  come  to  be  con- 
sidered in  a  general  way  as  a  measure  of  the  resistance  to  the  break- 
ing down  of  the  oil  film.  Jerome  Alexander.135  uses  the  expression 
"film"  to  denote  a  layer  of  fluid  on  the  solid  surface  of  the  order  of 
10~7  centimeters  in  thickness  and  states  that  with  a  true  lubricant 
the  facility  of  slipping  is  maximal  when  a  layer  of  such  excessive 
tenuity  separates  the  solid  faces  and  nothing  is  gained  by  increasing 
the  thickness  of  the  layer,  a  fact  experimentally  demonstrated  with 
castor  oil.  According  to  Alexander,  lubrication  depends  wholly  upon 
the  chemical  constitution  of  a  fluid,  and  the  fact  that  the  true  lubri- 
cant is  able  to  render  slipping  easy  when  a  film  of  only  about  one 
molecule  deep  is  present  on  the  solid  faces,  suggests  that  the  true  lubri- 
cant is  always  a  fluid  which  is  adsorbed  by  the  solid  face.  Alexander 
explains  the  superior  lubricating  power  of  graphite  in  oil  by  the  for- 
mation of  a  graphite  surface  on  the  metal  to  which  the  oil  adheres 
more  strongly  and  greater  pressure  is  therefore  required  to  break  down 
this  oil  film.  Similar  views,  supported  by  experimental  evidence,  have 
been  expressed  by  Stanton,  Archbutt  and  Southcombe  136  and  by  D.  R. 
Mountford.137  The  latter  believes  that  the  molecules  of  the  liquid 
enter  into  a  firm  "physico-chemical"  union  with  the  metallic  surfaces 
(or  "adsorption"  according  to  Alexander).  Using  a  friction  testing 
machine  of  the  Thurston  type  the  friction  coefficient  of  a  certain 
nineral  oil  was  reduced  from  0.0065  to  0.0042  by  the  addition  of 
2  per  cent  of  fatty  acids.  The  experiments  of  the  former  authors  were 
carried  out  at  the  National  Physical  Laboratory  and  they  conclude 
that  viscosity  is  not  the  only  or  the  most  important  factor  in  cases  of 
difficult  lubrication.  They  also  attribute  "oilness"  to  adhesion  or 
chemical  (?)  affinity  between  the  metal  and  the  lubricant.  In  their 
experiments  one  per  cent  of  the  fatty  acids  of  rape  oil  added  to  a 
mineral  oil  lowered  the  friction  coefficient  from  0.0047  to  0.0033  and 
60  per  cent  of  neutral  rape  oil  was  necessary  to  produce  the  same 
effect. 

Widespread  dissatisfaction  exists  with  the  present  methods  of  test- 
ing employed  to  determine  the  lubricating  value  of  oils  and  Dunstan 

I138  J.  Ind.  &  Eng.  Chem.  12,  436  (1920). 
™  Engineering,  108,  758   (1919)  ;  Chem.  Abs.  14,  491   (1920). 
13TProc.  Phys.  Soc.  London  32,  II,  1  (1920)  ;  Chem.  A&8.  1$,  1475   (1920)  ;  Wells  & 
Southcombe,  J.  Inst.  Petr.  Techn.  4,  219  (1918). 


580       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

and  Thole  138  have  recently  expressed  the  opinion  (shared  by  the  pres- 
ent writer) ,  that  no  method  has  yet  been  developed  which  gives  values 
which  express  rationally  or  accurately  the  lubricating  value  of  an  oil. 
The  friction  testing  machine  of  Thurston  is  designed  to  duplicate 
closely  conditions  actually  obtaining  in  practice,  but  the  friction  coeffi- 
cients so  obtained  are  'strictly  a  function  of  the  viscosity  and,  as 
pointed  out  by  Ubbelohde,  are  superfluous  if  the  viscosity  is  determined. 
A  device  for  testing  film  stability  under  variable  pressure  and  move- 
ment of  surfaces  would  appear  to  be  rational  and  might  do  much  to 
clarify  understanding  of  this  subject. 

It  is  commonly  stated  that  pressure  has  no  effect  upon  viscosity  but 
under  very  great  pressures  the  viscosity  of  mineral  oils  is  greatly 
altered.  Under  a  pressure  of  5  tons  per  square  inch  the  viscosity  of 
mineral  oils  increases  16-fold,  and  Bridgeman  139  noted  that  ordinary 
lubricating  oils  become  very  viscous  at  pressures  of  a  few  thousand 
atmospheres,  and  kerosene  at  10°  and  8,000  atmospheres  changes  to 
about  the  consistency  of  vaseline.  The  viscosity  of  mineral  and  fatty 
oils  increases  with  pressure  and  at  pressures  greater  than  800  kilo- 
grams per  square  centimeter  the  rate  of  change  is  very  great.  At 
1,000  kg.  per  sq.  cm.  mineral  oils  have  viscosities  ten  to  twenty-five 
times  the  viscosities  at  ordinary  atmospheric  pressure.140 

Solubility:  Most  petroleums  and  their  distillates  are  completely 
miscible  in  benzene,  carbon  bisulfide,  ether  and  chloroform.  Absolute 
alcohol  does  not  dissolve  crude  petroleums  completely  but  amyl  alco- 
hol dissolves  the  hydrocarbons,  leaving  asphaltic  matter  undissolved. 
Petroleums  containing  relatively  large  proportions  of  aromatic  hydro- 
carbons are  dissolved  by  solvents  such  as  alcohol  to  a  larger  extent 
than  other  petroleums.  Oils  containing  a  maximum  proportion  of 
paraffine  hydrocarbons,  such  as  light  Pennsylvania  oil,  are  generally 
least  soluble.  The  lighter  fractions  are  more  soluble  than  the  higher 
boiling  fractions.  In  the  following  table  the  "critical  solution  tem- 
perature" was  determined  by  heating  the  distillate  with  an  equal 
volume  of  the  solvent,  then  cooling  slowly  and  noting  the  temperature 
at  which  turbidity  appeared.141 

***J.  Inst.  Petr.  Techn.  4,  191   (1918). 
U9Proc.  Am.  Acad.  1ft,  345   (1911). 
"°Hyde,  Proc.  Roy.  Soc.  91  A,  240   (1920). 
141  Chercheffsky,  J.  Petr.  1910,  210. 


Grit.  Sol.  Temperature  °C 

acetic 

ethyl  ale.  96  £% 

anhydride 

50.° 

78.5 

68.5° 

91. 

87.° 

104.5 

36.° 

66. 

47.5° 

72. 

60.° 

79.5 

31.° 

60. 

53.° 

75.5 

72.5° 

89.5 

miscible  at  20° 

53. 

30.° 

57. 

42.° 

63.5 

PHYSICAL  PROPERTIES  581 

Sp.  Gr. 
Petroleum  oj  Fraction 

American  0.780 

(Pennsylvania)    0.800 

0.820 
Russian   0.780 

0.800 

0.820 
Galician    0.780 

0.800 

0.820 
Roumanian    0.780 

0.800 

0.820 

Although  paraffine  wax  has  been  a  common  commercial  product 
for  a  great  many  years  and  finds  most  varied  application  both  in  the 
industries  and  in  scientific  work,  very  little  information  has  been  pub- 
lished regarding  its  solubility  in  various  solvents  or  its  solvent  power 
for  other  substances.  The  following  table  gives  the  solubility  of  a 
hard  paraffine,  melting-point  64°-65°  (about  10°  higher  melting-point 
than  that  of  the  average  commercial  paraffine)  which  had  been  pre- 
pared from  ozokerite.  The  softer  waxes  are  probably  more  soluble 
tnan  the  sample  here  described.142 

g Paraffine  Wt.  oj  Solvent 

Dissolved  by  to  Dissolve  1 

Solvent  100  g.  100  cc.       Part  Paraffine 

C&    12.99  ....  7.6 

Light  petr.—  to  75  °C  — Sp.  Gr.  0.7233..  11.73  8.48  8.5 

Turpentine,  158°-160°   6.06  5.21  16.1 

Xylene,  commercial  135°-143°  3.95  3.43  25.1 

Toluene,  108.5°-109.5°    3.92  3.41  25.5 

Chloroform    2.42  3.61  41.3 

Benzene    1.99  1.75  50.3 

Ethyl  ether  1.95  ....  50.8 

Acetone    0.262  0.209  378.7 

Ethyl  acetate   0.238  419. 

Ethyl  alcohol,  99.5%   0519  ....  453 

Amyl  alcohol,  127°-129°   0.202  0.164  495. 

Methyl  alcohol   0.071  0.056  1447. 

Methyl  formate 0.060  ....  1648. 

Glacial  acetic  acid   0.060  0.063  1668. 

Acetic  anhydride   0.025  3956. 

Formic  Acid  (cryst.)   0.013  0.015  7689. 

A  comprehensive  discussion  of  the  problem  of  separating  paraffine 
wax  from  viscous  oils  by  the  use  of  solvents  has  recently  appeared, 
the  raw  material  investigated  being  the  oily  distillates  obtained  by 
the  distillation  of  shales  and  lignites  at  low  temperatures.  In  connec- 

"Tawlewski  and  Filemonowicz,  Ber.  £1,  2973  (1888). 


582       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

tion  with  this  work  the  solubility  of  paraffine  wax,  melting-point  56°, 
was  determined  in  mixtures  of  benzene  and  alcohol  at  ordinary  tem- 
peratures and  in  the  cold.143 

SOLUBILITY  OF  PARAFFINE:  GRAMS  IN  lOOcc.  SOLVENT. 

Solvent  23°  C  0°  —20° 

Acetone    0.27  0.06  0.02 

Benzene-alcohol,  2:8    0.48  0.10  0.01 

«  "         3:7 0.77  0.18  0.04 

4:6 1.14  0.23  0.05 

Alcohol,  94.5%   0.16  0.01  0.006 

Unsaturated  hydrocarbons  are  generally  more  soluble  than  satu- 
rated hydrocarbons  which  fact  is  utilized  in  their  separation  by  liquid 
sulfur  dioxide.  The  hydrocarbons,  including  unsaturated  hydrocar- 
bons are  very  much  less  soluble  in  ethyl  alcohol  than  alcohols,  alde- 
hydes, ketones  and  esters,  which  fact  is  made  use  of  in  the  manufacture 
of  terpene  and  sesquiterpene-free  essential  oils.  Very  few  data  bear- 
ing on  this  have  been  published  but  the  solubility  of  turpentine  and 
95  per  cent  alcohol  may  be  taken  as  a  typical  example  of  the  solu- 
bility of  this  type  of  hydrocarbon.144 

Temperature  of  Grams  of  95%  Alcohol 
Separation  °C  in  100  g.  Mixture 

20.7  2.4] 

42.2  3.4  }-  oil  rich  phase 

53.0  7.2J 

53.1  10.2^ 
44.0  20.3 

37.2  30.6 
29.6  48.3 

23.9  52.8  > alcohol  rich 

16.3  61.4          phase 
— 15.5  76.6 

—  24.  81.1 

—  63.  87.1  J 

Hexane  is  miscible  with  methyl  alcohol  at  42.8°. 145  The  effect  of  the 
hydroxyl  group  in  diminishing  the  solubility  of  a  substance  in  hydro- 
carbons explains  the  slight  solubility  of  castor  oil  in  lubricating  oils. 
The  solubility  of  castor  oil  in  gasolene,  which  is  of  some  technical  im- 
portance, is  very  much  like  the  behavior  of  aniline  and  the  simpler 
paraffines.  Castor  oil  is  usually  stated  to  be  insoluble  in  gasolene  but 
Atkins  finds  that  it  is  miscible  with  isohexane  at  40.8°,  with  octane  at 
47.8°  and  that  it  is  miscible  at  ordinary  tempertaures  in  certain  gaso- 

143  Seidenschnur,  Brennstoffchem.  2,  49,  73,  81    (1920). 
14*Vezcs  &  Mouline,  Butt.  .soc.  chim.    (3)   31.  1043    (1904). 
"5  Rothmund,  Z.  physik.  Chem.  26t  433   (1898). 


PHYSICAL  PROPERTIES  583 

lenes  rich  in  naphthenes  such  as  that  from  Roumanian  and  Galician 
petroleum.146  Aniline  and  aliphatic  hydrocarbons  are  iniscible  when 
warmed  but  separate  into  two  phases  when  chilled.  Thus  amylene 
and  aniline147  are  miscible  at  temperatures  above  14.5°. 

Grams  Aniline  in  100  g. 

Amylene  Aniline 

Tempo.  °C                                             Layer  Layer 

0                              19.5  "81.5 

4                                                  ...       20.5  79.5 

8                .'.'.' 24.2  75.8 

10                              28.  73. 

12 34.  68. 

14 45.  59. 

14.5   miscible 

The  normal  hydrocarbons,  pentane,  hexane,  heptane  and  octane,  are 
miscible  with  aniline148  at  72°,  69°,  70°  and  72°  respectively,  cyclo- 
pentane  at  18°  and  cyclohexane  at  31°. 

Crude  petroleum  oils  contain  considerable  dissolved  methane, 
ethane  and  propane  and  on  heating  or  distilling  the  oil  these  dissolved 
gases  are  not  immediately  expelled.  Markownikow  showed  that  kero- 
sene and  a  sample  of  machine  oil  (Sp.  Gr.  0.906)  dissolved  about  220 
volumes  of  isobutylene  at  ordinary  temperatures  and  that  the  gas  was 
completely  expelled  only  after  heating  to  about  260°.  Unsaturated 
gaseous  hydrocarbons,  ethylene  and  propylene  are  dissolved  from  oil 
gas  by  compressing  with  heavy  oil  to  a  greater  extent  than  the  satu- 
rated hydrocarbons  which  accompany  these  olefines  in  oil  gas,  and  on 
heating  or  applying  diminished  pressure  to  the  heavy  oil  solution  the 
evolved  gas  is  accordingly  richer  in  olefines.  Russian  kerosene  dis- 
solves 0.144  volume  of  methane  and  0.164  volume  of  ethylene  at  10° 
and  atmospheric  pressure.  McDaniel 149  has  determined  the  solubil- 
ities of  methane,  ethane,  and  ethylene  in  ten  organic  solvents  at  tem- 
peratures from  20°  to  60°.  The  solvents  in  the  order  of  increasing 
solvent  power  for  methane  at  25°  are  methyl,  amyl,  ethyl,  isopropyl 
alcohols,  benzene,  toluene,  m-xylene,  hexane  and  heptane.  With 
ethane  and  ethylene  the  same  solvents  fall  into  a  similar  series  in  the 
same  order.  Contrary  to  Just150  McDaniels  finds. that  the  solubil- 
ities of  these  solvents  for  nitrogen,  oxygen  and  carbon  dioxide  do  not 
follow  in  the  same  order  as  in  the  case  of  the  hydrocarbons.  Ethylene 
is  more  soluble  in  water  than  in  kerosene151  (water  dissolves  0.149 

146  J.  Inst.  Petr.  Technologists,  6,  223   (1920). 

14T  Konowtilow,  Ann.  physik.   (4)   10,  375    (1903). 

""Chavanne  &  Simon,  Compt.  rend.  168,  1111  (1919). 

149 «/.  Phys.  Chem    15,  587   (1911). 

160  Z.  physik.  Chem.  37,  342    (1901). 

151Gniewosz  &  Walfisz,  Z.  physik.  Chem.  1889,  70. 


584       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

volumes  of  ethylene  at  20°).  According  to  Charitschkow,152  care- 
fully refined  kerosene  dissolves  more  ammonia  at  22°,  0.4982  volumes, 
than  at  0°. 

The  solvent  power  of  compressed  gases  for  certain  solids  and 
liquids  having  very  low  vapor  pressures  is  a  fact  frequently  over- 
looked. A  compressed  gas  has  noticeable  solvent  power  for  such  a 
solid  or  liquid  only  when  the  gas  compressed  to  the  liquid  state  is  of 
such  a  character  as  to  dissolve  the  solid  or  liquid  to  a  marked  degree, 
and  when  one  recalls  that  the  physical  properties  of  gas  and  liquid 
become  identical  at  the  critical  point  it  becomes  evident  that  the  solu- 
bility curves  of  gas  and  liquid  must  merge  smoothly  into  each  other  at 
the  critical  point.  Ethyl  chloride  dissolves  in  5  to  6  volumes  of 
methane  under  180  atmospheres  pressure,  at  17°,  and  at  200  atmos- 
pheres the  two  Become  miscible  and  the  surface  separating  gas  and 
liquid  phases  disappears.  Iodine,  camphor  and  paraffine  wax  dissolve 
in  compressed  methane  to  a  marked  extent  and  on  releasing  the  pres- 
sure the  paraffine  wax  is  deposited  again.  Compressed  ethylene  also 
has  a  very  marked  solvent  power  for  paraffine  wax  and  stearic  acid.153 
Cyclohexane  has  been  proposed  as  a  cryoscopic  solvent  but  is  un- 
reliable for  this  purpose  on  account  of  the  tendency  of  substances 
containing  hydroxyl,  carboxyl,  carbonyl  or  nitro  groups  to  associate 
in  this  solvent.154  Iodine  is  less  soluble  in  cyclohexane  than  in  ben- 
zene.155 

Hexane  generally  has  less  solvent  power  than  benzene.  One  hun- 
dred grams  of  the  former  dissolves  0.37  grams  of  anthracene  at  25°, 
as  compared  with  1.86  grams  in  benzene.  Ligroin,  100  g.,  dissolves 
0.72  g.  benzoic  acid  at  16°  and  turpentine  dissolves  5.09  grams  (at 
25°).  Sulfur  is  markedly  soluble  in  hexane,  as  indicated  in  the  fol- 
lowing table, 

SOLUBILITY  OF  SULFUR  IN  HEXANE.IM 

Temp.  °C  g.S.  in  100  g.  Solution 

—  20  0.07 

0  0.16 

20  0.25 

40  0.55 

60  1.0 

80  1.7 

100  2.8 

120  4.4 

130  5.2 

140  6.0 

Bakuer   Teclvn.    Ges.   1893,  5;    Gurwitsch    (Wiss.    Grundl,   d.    Erdolbearb, 


1913,  100. 

1MVillard,  Chem.  News,  78,  297,  309   (1898). 

1M  Mascarelli,  Atti  accad.  Lincei   (5)   17,  494. 

165  Bruni,  Oazz.  chim.  Ital.  42,  12. 

1MEtard,  Ann.  chim.  phys.   (7)  2,  526;  3,  275   (1894). 


PHYSICAL  PROPERTIES  585 

The  true  solubility  of  sulfur  in  organic  solvents  is  frequently  dif- 
ficult to  determine  on  account  of  the  fact  that  sulfur  frequently  forms 
colloidal  solutions,  as  in  the  now  well-known  example  of  colloidal 
sulfur  in  [3.|3-dichloroethyl  sulfide.157  The  solubility  of  sulfur  in  the 
hydrocarbon  caoutchouc  has  been  such  a  case,  further  complicated  by 
the  fact  that,  on  warming,  the  sulfur  is  able  to  combine  chemically 
with  the  double  bonds  of  the  hydrocarbon.  Also,  sulfur  appears  to 
be  more  soluble  in  organic  substances  containing  one  or  more  chemi- 
cally bound  sulfur  atoms  and  Skellon158  finds  that  as  the  per  cent 
of  chemically  bound  sulfur  in  vulcanized  rubber  increases,  the  solu- 
bility for  sulfur  as  free  sulfur  increases.  Thus  ebonite  may  contain  a 
greater  proportion  of  free  sulfur  than  soft  cured  rubber  and  still  not 
bloom.  Loewen 159  observed  the  solution  of  sulfur  in  rubber  under  a 
microscope  and  noted  that  when  the  time  of  "vulcanization"  is  short, 
droplets  of  melted  sulfur  are  visible;  on  continued  heating  the  mix- 
ture clears  up  and  the  droplets  disappear  but  on  cooling  sulfur  glob- 
ules may  reappear.  If  the  time  of  heating  be  a  little  longer  than 
in  the  last  case,  there  is  not  sufficient  free  sulfur  in  solution  to  form 
droplets  on  cooling  but  crystalline  sulfur  may  slowly  separate  on 
standing.  If  the  time  of  vulcanization  is  still  further  prolonged,  no 
free  sulfur  will  separate  after  cooling. 

The  viscosities  of  rubber  solutions  in  chlorinated  solvents  are 
approximately  double  the  viscosities  of  solutions,  of  the  same  con- 
centration, in  gasolene  or  benzene,  but,  after  heating,  all  kinds  of 
rubber  solutions  have  about  the  same  viscosity.160  Gaunt  finds  that 
the  viscosities  of  fine  hard  Para  rubber  in  various  solvents,  in  order 
of  decreasing  viscosity,  are  as  follows,  benzene,  CHC13,  gasolene,  ethyl 
ether.161  Gaunt  assumes  that  such  rubber  solutions  contain  aggre- 
gates of  rubber  micelles  and  that  heating,  mechanical  working  of  the 
rubber  or  other  processes  which  break  up  these  aggregates,  or  which 
cause  depolymerization,  decrease  the  viscosity.  A  ten  per  cent  solu- 
tion of  raw  Para  rubber  in  amyl  acetate  is  fluid  enough  to  filter 
through  ordinary  filter  paper.  Acetone  is  soluble  in  rubber  to  the 
extent  of  about  17  per  cent.  Rubber  may  be  precipitated  from  ben- 
zene or  ether  solutions  by  the  addition  of  alcohol  or  acetone.  Tetra- 
hydronaphthalene  is  said  to  have  marked  solvent  power  for  rubber. 

157  Wilkinson,  Neilson  &  Wylde,  J.  Am.  Chem.  Soc.  42,  1377   (1920). 

158  India  Rubber  J.  1,6,  723  (1913). 
™»Gummi  Ztg.  27,  1301    (1913). 

10"Kirchoff,   Caoutsch  d  gutta-percha  12,  8649   (1915). 
181  India  Rubber  J.  47,  1054,  1093. 


586       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

Liquid  sulfur  dioxide  readily  dissolves  aromatic  and  unsaturated 
hydrocarbons  but  saturated  non-benzenoid  hydrocarbons  are  only  very 
slightly  soluble  in  this  solvent.  Edeleanu  162  has  developed  a  refining 
method  based  upon  these  facts.  The  method  has  found  greater  favor 
in  Europe  than  in  America,  although  kerosene  refined  in  this  way  has 
a  lower  specific  gravity  and  usually  better  burning  qualities  than 
kerosene  refined  by  sulfuric  acid.  The  unsaturated  and  aromatic 
hydrocarbons  are  easily  separated  by  distillation  from  the  low  boil- 
ing sulfur  dioxide  but  the  oils  thus  recovered  have  not  yet  proven  to 
be  of  special  industrial  value.  The  fraction  boiling  at  150°-200°  has 
been  recommended  as  a  turpentine  substitute.  With  many  oils  the 
liquid  sulfur  dioxide  method  does  not  yield  water-white  oils,  and  in 
such  cases  refining  with  small  proportions  of  sulfuric  acid  must  be 
resorted  to  in  order  to  get  this  result.  The  separation  of  the  aro- 
matic and  unsaturated  hydrocarbons  from  the  paraffines  is  much  more 
efficient  at  low  temperatures,  a  temperature  of  about  — 12  °C  being 
recommended.  The  method  readily  lends  itself  to  analytical  sepa- 
rations and  has  been  checked  by  Egloff,  Moore  and  Morrell.163  Ben- 
zene, toluene,  and  xylenes  and  mesitylene  are  completely  miscible  with 
this  solvent  at  — 10°  and  when  using  33  and  66  per  cent  by  volume 
of  liquid  sulfur  dioxide  at  — 18°  the  pentane,  hexane,  octane,  monane 
and  decane  fractions  and  gasolene  from  light  Pennsylvania  petroleum 
are  practically  insoluble.  At  — 10°,  using  the  same  proportions  of 
solvent,  these  paraffines  are  soluble  to  the  extent  of  about  1.8  per  cent. 
Pennsylvania  kerosene  was  found  to  be  3.6  per  cent  soluble  at  — 10°, 
using  66  per  cent  by  volume  of  the  solvent.  Amylenes  are  completely 
miscible  at  — 10°  and  — 18°.  Cyclohexane  is  insoluble  at  — 18° 
and  3  per  cent  soluble  in  an  equal  volume  of  sulfur  dioxide  at  — 4.5°, 
and  naphthenes  of  higher  boiling-point,  following  the  general  order 
of  solubility  noted  above,  are  less  soluble  than  cyclohexane. 

The  Non-benzenoid  Hydrocarbons  and  Colloid  Phenomena. 

A  very  large  number  of  organic  substances  are  much  more  spar- 
ingly soluble  in  petroleum  ether  than  in  ethyl  ether  or  other  organic 
solvents  and  this  fact  accounts  for  the  wide  employment  of  mixtures 
of  petroleum  ether  and  ethyl  ether  in  recrystallizing  organic  substances 
in  laboratory  research  work;  the  ethyl  ether  evaporates  more  rapidly 

162  German  Pat.  216,459;  Petroleum  9,  862  (1914)  ;  Engler  &  ubbelohde,  Z.  angew. 
Chem.  1913,  177. 

188  Met.  &  Chem.  Eng.  18,  396    (1918). 


PHYSICAL  PROPERTIES  587 

and  the  substance  crystallizes  from  the  solvent  mixture  as  it  becomes 
continually  richer  in  petroleum  ether.  However,  when  a  high  degree 
of  supersaturation  is  quickly  brought  about,  as  by  pouring  a  warm 
one  to  two  per  cent  solution  of  stearic  acid  in  gasoline,  into  a  solution 
of  a  little  sodium  ethylate  in  gasoline,  the  whole  quickly  sets  to  a 
jelly. 

Numerous  attempts  have  been  made  to  prepare  stable  petroleum 
jellies,  or  "solidified  petroleum."  The  sodium  stearate  jellies  are  not 
very  firm  and  soon  begin  to  exude  oil,  according  to  the  well-known 
phenomenon  of  syneresis,  common  to  all  jellies  of  this  type.  Other 
more  or  less  solid  preparations  of  petroleum  oils  are  really  emul- 
sions.164 A  high-melting  wax  is  sometimes  added  .to  stiffen  the  jelly 
and  one  patentee  adds  about  15  per  cent  of  turpentine  in  order  to  get 
a  larger  proportion  of  alkali  stearate  into  solution  when  warm.  An- 
ther patentee  prepares  an  emulsion  with  gelatin  which  is  then  hard- 
ened by  formaldehyde.165 

Calcium  soaps,  when  dry,  give  clear  solutions  with  mineral  oils, 
gelatinizing  on  cooling.  On  stirring  in  water  emulsification  and  stif- 
fening of  the  grease  results.  Commercial  greases  frequently  contain 
up  to  22  per  cent  of  calcium  soaps.166 

Colloids  containing  mostly  soap  and  a  little  mineral  oil  are  manu- 
factured and  known  usually  as  naphtha  soaps.  The  presence  of  free 
fatty  acid  or  unsaponified  fatty  oil  assists  in  preventing  the  separa- 
tion of  the  petroleum  oil.167 

The  solubility  of  soaps  in  mineral  oils  increases  rapidly  with  in- 
creasing molecular  weight  of  the  fatty  acid,  but  in  light  petroleum 
ether  the  lead  soaps  are  very  sparingly  soluble,  100  cc.  of  the  hydro- 
carbon dissolving  0.0528  g.  lead  heptoate,  0.221  g.  lead  myristate  and 
0.017  g.  lead  stearate.168 

The  subject  of  emulsions  lies  somewhat  far  afield  from  the  subject 
matter  and  purpose  of  the  present  volume  but  anyone  working  with 
the  non-benzenoid  hydrocarbons  is  apt  to  be  concerned  with  emul- 
sions of  various  types  and  a  limited  number  of  examples  will  there- 
fore be  briefly  mentioned.  The  theory  of  emulsions  has  been  very 

164  Kuess,  J.  Soc.  Chem.  Ind.  1906,  1141.     Ten  parts  of  stearin  are  combined  with 
9  parts  caustic  soda  in  18  parts  of  water  and  100  parts  of  kerosene  stirred  in,  melted 
at  105°-115°  and  the  alkali  soap  converted  into  the  more  insoluble  Al  or  Mg  soaps  by 
adding  magnesium   or   aluminum  sulfate. 

165  van  der  Heyden,  J.  Soc.  Chem.  Ind.  1906,  236.     For  a  general  review  see  Behrend, 
Kunstoffe.  1911,,  356. 

18«Cf.  Holde,  Z.  Chem.  Ind.  Roll.  3,  270   (1908). 

""Brit.  Pat.  2,137   (1911)  ;  Chem.  Abs.  6,  2014   (1912)  ;  8,  1026   (1914). 

1B8Neave,  Analyst  37,  399    (1912). 


588       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

thoroughly  reviewed  by  Bancroft.169  The  emulsifying  power  of  fatty 
acid  soaps,  for  mineral  or  other  oils,  is  well  known  but  the  sulfonic 
acid  derivatives  of  petroleum  hydrocarbons  or  their  alkali  salts,  also 
possess  this  property  to  a  high  degree.  The  removal  of  these  sul- 
fonic acids  from  the  treated  oil  by  washing  first  with  water  and  then 
with  alkali,  without  undue  loss  of  hydrocarbon  oils,  is  one  of  the 
arts  of  the  petroleum  refiner.  One  of  the  most  troublesome  diffi- 
culties encountered  by  the  refiner  is  the  emulsification  of  water  in  oil, 
and  this  is  particularly  liable  to  occur  in  the  manufacture  of  highly 
refined  water  white  oils  of  the  so-called  liquid  paraffine  type.  Also, 
when  water  is  added  to  a  heavy  lubricating  oil  containing  a  lime  soap 
the  water  becomes- dispersed  in  the  oil  and  will  change  it  to  a  grease. 
As  pointed  out  by  Bancroft,  an  emulsifying  agent  is  a  substance  which 
goes  into  the  interface  and  produces  a  film;  if  the  adsorption  of  the 
emulsifying  agent  lowers  the  surface  tension  on  the  water  side  of  the 
interface  more  than  it  does  on  the  oil  side,  the  interface  will  tend  to 
curve  so  as  to  be  convex  on  the  water  side,  and  we  shall  have  a  ten- 
dency to  emulsify  oil  in  water.  If  the  adsorption  of  the  emulsifying 
agent  lowers  the  surface  tension  on  the  oil  side  of  the  interface  more 
than  it  does  on  the  water  side,  the  interface  will  tend  to  curve  so  as 
to  be  concave  on  the  water  side,  and  we  shall  have  a  tendency  to 
emulsify  water  in  oil. 

Pickering  17°  has  described  experiments  on  the  emulsification  of 
kerosene  in  fungicidal  and  insecticidal  sprays,  the  oil  being  emulsi- 
fied with  water  and  lime  or  basic  copper  sulfate.  The  oil  globules 
in  such  an  emulsion  are  probably  prevented  from  coalescing  by  being 
enveloped  in  a  pellicle  consisting  of  particles  of  the  solid  much  more 
minute  than  the  globules  themselves.  "Apparently  a  precipitate  con- 
sisting of  any  insoluble  substance  which  is  wetted  more  easily  by 
water  than  by  oil,  if  in  a  sufficiently  fine  state  of  division,  will  equally 
act  as  an  emulsifier."  Emulsions  made  with  such  an  insoluble  emul- 
sifier  are  in  every  respect  similar  to  those  made  with  soap  and  the 
like.  Quite  recently  emulsions  of  heavy,  nearly  non-volatile  oils 
have  been  prepared  in  casein  solutions:  these  solutions  can  then  be 
dried  by  spraying  in  a  vacuum  and  the  result  is  a  flour,  each  globule 
of  oil  being  protected  by  a  film  of  dried  casein.  Flours  have  been 
made  in  this  way  containing  as  much  as  85  per  cent  of  oil.  Other 
emulsions  can  probably  be  dried  in  the  same  manner.  Apparently  no 

189  J.  Phya.  Chem.  16,  177,  345,  475,  739   (1912)  ;  11,  501   (1913). 
"oj.   Chem.  Soc.  91,  2001    (1907). 


PHYSICAL  PROPERTIES  589 

industrial  applications  of  this  process  have  as  yet  been  made  in  the 
case  of  mineral  oils. 

Adsorption  phenomena  are  of  more  than  academic  interest.  The 
highly  adsorptive  charcoals,  particularly  coconut  charcoal,  activated 
by  superheated  steam,  which  were  developed  during  the  war  for  the 
manufacture  of  military  gas  masks,  have  proven  to  be  highly  effi- 
cient in  selectively  adsorbing  the  vapors  of  liquid  hydrocarbons  from 
natural  gas.171  Good  "fifty  minute"  charcoal  will  adsorb  ten  to  fif- 
teen per  cent  of  its  own  weight  of  gasoline  vapors.  The  charcoal 
granules  employed  are  about  8  to  14  mesh  and  when  saturated  with 
adsorbed  hydrocarbons  the  latter  are  expelled  by  superheated  steam 
at  about  250°C. 

The  selective  adsorption  of  coloring  matter  from  vaseline  and 
lubricating  oils  by  fuller's  earth  has  long  been  known.  When  unre- 
fined black  vaseline  is  filtered  through  warm  fuller's  earth  the  first 
product  is  a  perfectly  fluid  oil  and  the  successive  portions  which  come 
through  are  progressively  more  and  more  viscous.  This  induced 
Day  172  to  subject  a  crude  petroleum  to  similar  treatment  and  it  was 
found  that  the  first  liquid  to  come  through  the  column  of  fuller's 
earth  consisted  of  light  low  boiling  hydrocarbons.  Day  realized  the 
significance  of  these  facts  and  stated  that  in  this  way  petroleum  in 
passing  through  strata  of  clay  and  fine  sand  could  be  greatly  altered ; 
asphaltic  matter,  if  originally  present,  could  in  this  way  be  removed 
by  adsorption  resulting  in  light  petroleum  of  the  Pennsylvania  type. 
His  views  were  communicated  to  the  Petroleum  Congress  held  in 
Paris  in  1900  and,  shortly  after,  Engler173  confirmed  Day's  experi- 
ments. The  subject  was  further  investigated  by  Gilpin  and  Cram,174 
who  liberated  the  oil  in  different  sections  of  the  fuller's  earth  columns 
by  the  addition  of  water.  They  found  that  the  lighter  fractions 
showed  less  loss,  on  treating  with  concentrated  sulfuric  acid,  than 
the  heavier  more  viscous  fractions  which  were  more  strongly  adsorbed 
and  they  interpreted  this  to  mean  that  unsaturated  hydrocarbons 
were  selectively  adsorbed  by  the  fuller's  earth.  This  would  indicate 
that  the  crude  oil  employed  by  them  contained  large  proportions  of 
unsaturated  hydrocarbons,  which  is  extremely  improbable.  As  to 
whether  or  not  unsaturated  hydrocarbons  are  selectively  adsorbed  by 
fuller's  earth  has  not  definitely  been  shown. 

1T1Burrell,  Oberfell  &  Voress,  Chem.  d  Met.  Eng.  24,  156   (1921). 
172Proc.  Am.  Phil.  Soc.  56,  154    (1897). 
"3  Z.  angew.  chem.  1901,  889. 
"'Am.  Chem.  J.  40,  495    (1908). 


590       CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

Continuing  these  investigations  Gilpin  and  Bransky  175  pointed  out 
that  it  is  not  necessary  to  assume  a  vegetable  origin  for  petroleums 
of  the  light  Pennsylvania  type.  The  petroleum  found  in  the  Trenton 
limestone  is  supposed  to  have  been  derived  from  organic  remains 
buried  in  this  strata,  as  indicated  by  the  abundance  of  fossil  remains 
found  in  this  limestone,  and  this  supposition  is  supported  by  the  rela- 
tively large  proportions  of  sulfur  and  nitrogenous  compounds  in  this 
oil.  By  filtration  of  oils  such  as  the  Ohio-Trenton,  California  and 
Texas  petroleums  through  a  bed  of  fuller's  earth,  oils  very  similar 
to  light  Pennsylvania  petroleum  can  be  obtained.  Any  sufficiently 
fine  grained  and  porous  material  is  capable  of  absorption,  to  a  greater 
or  less  degree,  just  as  in  the  case  of  fuller's  earth.  Beaumont,  Texas, 
petroleum  containing  1.75  per  cent  sulfur,  on  passing  through  a  kaolin 
filter  gave  a  fraction  containing  0.70  per  cent  sulfur.178  In  a  later 
paper  Gilpin  and  Schneeberger 177  showed  that  sulfur  and  nitrogen 
derivatives  were  selectively  adsorbed  from  a  heavy  petroleum  from 
Kern  County,  California.  By  two  filtrations  of  this  oil  they  obtained 
the  following: 

Sp.  Gr.  %  Sulfur 

Crude  oil  0.912  0.541 

Fraction  A  (1)  0.857  0.06 

A  (2)   0.8604  0.07 

A  (3)    0.869        .  0.104 

B  (1)   0.862  0.072 

B  (2)   0.8771  0.09 

B  (3)   0.8803  0.141 

One  filtration  gave  the  following  results  with  respect  to  nitrogen, 

Sp.  Gr.  %  Nitrogen 

Crude  oil  0.889  0.761 

Fraction  (1)   ...' 0.8264  0.08 

(2)   0.8421  0.116 

(3)    0.852  0.289 

(4)   0.8614  0.315 

(5)   0.8737  0.332 

A  similar  filtration  of  another  sample  of  California  petroleum  of  Sp. 
Gr.  0.9118  and  boiling  over  the  range  105°-340°  gave  fractions  vary- 
ing from  the  lightest,  Sp.  Gr.  0.8325,  boiling-point  160°-195°  to  a 
fraction  Sp.  Gr.  0.8984  and  boiling-point  329°-340°. 

178  Am.   Chem.  J.  44,  251    (1910). 

"'Richardson  &  Wallace,  J.  Soc.  Chem.  Ind.  1902. 

177  Am.  Chem.  J.  50,  59    (1913). 


Chapter  XVII.     Physiological  and 
Related  Properties 

Odor:  The  physiology  of  odor  is  exceedingly  obscure.  However 
some  generalizations  can  be  made  with  reference  to  the  relation  be- 
tween chemical  constitution  and  odor.  The  odor  of  a  substance  ap- 
pears to  be  a  property  of  the  whole  molecule,  but  is  greatly  affected 
by  the  presence  or  absence  of  certain  groups  and  also  by  the  relative 
positions  of  different  groups.  Thus,  the  odor  of  the  unsaturated 
ketones  isomeric  with  a-ionone  (q.v.)  is  markedly  affected  by  each 
change  in  the  position  of  the  double  bond  in  the  ring  and  by  the 
positions  of  the  methyl  group,  with  reference  to  the  ketonic  side  chain. 
The  marked  difference  in  odor  between  isomeric  normal,  secondary 
and  tertiary  alcohols  is  well  known. 

Many  of  the  saturated  non-benzenoid  hydrocarbons  have  faint 
but  more  or  less  characteristic,  rather  agreeable  odors.  Methane  and 
ethane  are,  to  most  persons,  entirely  odorless  but  the  pentanes  and 
other  comparatively  volatile  hydrocarbons  have  odors,  and  many 
hydrocarbons  having  the  group  — C(CH3)3  or  — CH(CH3)2  have 
camphor  like  odors,  as  do  the  aliphatic  tertiary  alcohols.  The  light 
fraction  from  the  petroleum  of  the  Jennings-Louisiana  field  and  the 
gasolene  obtained  from  the  natural  gas  of  the  Houma-Louisiana  field 
contains  saturated  hydrocarbons  whose  odor  closely  resembles  turpen- 
tine. Unsaturated  hydrocarbons  have  somewhat  more  pronounced 
odors  than  the  corresponding  saturated  hydrocarbons  but  still  much 
less  intense  than  alcohols,  esters,  ketones,  aldehydes,  etc.  The  offen- 
sive odor  of  unrefined  gasolines,  particularly  when  made  by  cracking 
processes,  has  erroneously  been  attributed  to  unsaturated  hydrocar- 
bons but  the  malodorous  constituents  in  such  oils  are  naphthenic  acids 
and  derivatives  containing  sulfur  or  nitrogen.  The  older  idea  is 
accounted  for  probably  by  the  notion  that  refining  by  sulfuric  acid 
consists  merely,  or  essentially,  in  removing  unsaturated  hydrocarbons. 
Certain  conjugated  dienes,  for  example  cyclohexadiene,  and  the  light 
condensate  obtained  on  compressing  Pintsch  gas  containing  cyclo- 

591 


592      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

hexadiene  and  probably  cyclopentadiene,  possess  sharp  pungent  odors 
when  strongly  inhaled.  Diallyl  has  an  odor  resembling  horse-radish 
and  the  effect  of  the  double  bond  in  changing  the  odor  of  propyl  alco- 
hol and  propionic  aldehyde  to  the  very  sharp  irritating  odors  of  allyl 
alcohol  and  acrolein,  is  well  known.  These  examples  also  illustrate 
the  fact  that  odor  is  a  property  of  the  whole  molecule,  not  a  blend  or 
composite  odor  of  the  constituent  groups;  thus  the  double  bond  in 
propylene  is  practically  odorless,  and  propyl  alcohol  and  propionic 
aldehyde  are  quite  without  the  sharp  irritating  properties  of  acrolein 
and  allyl  alcohol. 

Cyclic  unsaturated  hydrocarbons  such  as  the  terpenes  and  ses- 
quiterpenes  have  sweet  agreeable  odors.  Fresh  turpentine  or  pure 
pinene  is  sweet  and  agreeable  in  odor  and  the  irritating  offensive 
odor  of  the  stored  or  oxidized  product  is  due  to  formic  acid  and  other 
oxidation  products.  Ring  closing  has  very  little  effect  upon  odor,  as, 
for  example,  n.hexane  and  cyclohexane,  secondary  hexyl  alcohol  and 
cyclohexanol ;  when,  however,  the  closing  of  the  ring  affects  the  con- 
stitution, as  in  the  conversion  of  an  aldehyde  group  to  a  hydroxyl 
group  the  change  in  odor  is  pronounced. 

Intensity  of  odor  can  hardly  bear  any  relation  to  chemical  stability 
as  we  find  stable  borneol,  having  a  strong  pepper  and  camphor-like 
odor,  and  ce-terpineol,  which  readily  decomposes,  has  a  very  faint 
odor,  and  many  other  illustrations  of  this  relation  could  be  given. 
Also  mercaptans  are  not  appreciably  different  from  alcohols  in  stabil- 
ity but  their  odors  are  beyond  comparison.  It  should  be  noted,  how- 
ever, that  we  are  probably  handicapped,  in  attempting  to  make  com- 
parisons and  generalizations,  by  the  fact  that  we  can  know  only  what 
the  human  nose  tells  us,  and  this  we  can  only  very  imperfectly  de- 
scribe or  record.1 

The  subject  of  odor,  while  seldom  mentioned  in  chemical  texts 
and  reviews,  is  given  attention  in  these  pages  as  it  is  a  sense  which 
is  exceedingly  useful  to  organic  chemists.  In  many  cases  impurities 
can  be  detected  with  reasonable  certainty  by  means  of  the  nose  when 
chemical  tests  fail  or  are  not  sufficiently  delicate. 

Physiological  Action:  Strictly  speaking,  the  saturated  hydrocar- 
bons cannot  be  said  to  have  any  physiological  properties,  although 
inhalation  of  the  vapors  of  the  more  volatile  ones  quickly  produce 
drowsiness,  followed  by  anesthesia,  and,  in  extreme  cases,  death  by 

»Cf.  Henning,  "Der  Geruch,"  Lelpslg,  1916. 


PHYSIOLOGICAL  AND  RELATED  PROPERTIES  593 

asphyxiation  may  result.2  Workers  in  paraffine  wax  plants  frequently 
develop  skin  sores  which  are  supposed  to  be  due  to  the  closing  of  the 
skin  pores  by  the  wax.  The  value  of  soft  flexible  paraffine  as  a  coat- 
ing over  burns  *is  merely  that  of  a  non-irritant  mechanical  protection, 
protecting  the  tissue  from  the  air,  temperature  changes,  and  giving 
the  growing  new  tissue  mechanical  support.  The  saturated  hydro- 
carbons are  not  attacked  by  oxidizing  enzymes  or  other  active  body 
fluids  and  accordingly  are  entirely  inert  in  the  digestive  tract. 

Viscous,  water-white,  tasteless  mineral  oils  are  widely  sold  for 
pharmaceutical  purposes,  under  a  variety  of  names,  i.  e.,  paraffinum 
liquidum,  liquid  petrolatum,  paraffine  oil  and  many  special  trade 
names.  As  has  been  pointed  out  by  Marcusson  most  oils  of  this  class 
contain  no  paraffine  whatever  but  consist,  like  lubricating  oils  from 
which  they  are  in  fact  made  by  drastic  refining,  of  cyclic  hydrocar- 
bons of  the  so-called  naphthene  or  polynaphthene  class,  CnH2I1_2,  and 
CnH2D  _  4.  Such  an  oil  examined  by  Marcusson 3  had  the  specific  gravity 

20° 

—  of  0.8827  and  showed  the  following  analysis, 

Found         Calculated  for  C*>H» 

Carbon    86.74%  86.33% 

Hydrogen    13.43  13.67 

The  freezing  test,  by  which  small  proportions  of  paraffine  may 
separate,  if  present,  may  serve  to  differentiate  between  oils  made  from 
paraffine  base  crudes,  and  those  made  from  paraffine-free  oils  such  as 
Russian  Baku,  California  or  Gulf  Coast  crudes,  but  its  presence  is 
hardly  to  be  condemned  since  if  the  paraffine  does  not  separate  at  room 
temperatures,  it  certainly  could  not  do  so  in  the  body.  Bastedo* 
reports  a  clinical  investigation  of  Russian  and  American  oils  and 
states  that  the  choice  between  different  oils  of  these  types  is  an  open 
one  "to  be  determined  by  palatability,  depending  upon  the  degree 
to  which  the  refinement  has  been  carried  out."  Bastedo  agrees  with 
the  original  recommendation  of  Sir  Arbuthnot  Lane  that  oils  for  inter- 
nal use  should  have  a  specific  gravity  of  not  less  than  0.885,  on  account 
of  low  viscosity  and  leakage.  Exposure  to  sunlight  in  loosely  stop- 
pered bottles  will  develop  taste  and  odor  in  from  4  to  10  days  and 
often  serves  to  differentiate  between  the  quality  of  oils  of  equal 
palatability  when  freshly  prepared.5  Various  chemical  tests  have 

2Fuhner,  Biocliem.  Z.  115,  235   (1921). 
3  Chem.  Ztg.  1913,  550. 

*«/.  Am.  Med.  Assoc.  March  6,  1915,  p.  808. 
•Brooks,  J.  Am.  Med.  Assoc.  65,  24   (1916). 


594      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

been  proposed  to  determine  quality,  which  are  of  more  or  less  value 
in  eliminating  the  personal  equation  involved  in  testing  by  taste  and 
odor.  Good  oils  on  treating  with  concentrated  sulfuric  acid  at  room 
temperature  will  not  be  colored  more  than  pale  straw  yellow  in  5 
minutes. 

Unsaturated  hydrocarbons,  ethylene,  propylene,  butylene  and  the 
amylenes,  act  upon  the  nerve  centers  producing  first  excitement  and 
then  narcosis.  Amylene  was  proposed  as  an  anesthetic  by  Snow  in 
1856,  but  it  was  found  to  be  dangerous,  due  to  sudden  failure  of  car- 
diac motion.  Its  use  was  condemned  by  the  French  Academy  soon 
after  its  introduction.  Gwathmy  6  notes  two  deaths  in  238  adminis- 
trations. The  liquid  unsaturated  hydrocarbons  are  mildly  irritating 
to  the  skin  and  mucous  membranes.  Taken  internally  unsaturated 
hydrocarbons  cause  severe  gastric  irritation  and  may  even  lead  to 
convulsions  and'  death.  The  higher  aliphatic  alcohols,  such  as  sec- 
ondary octyl  alcohol,  geraniol  and  the  terpene  alcohols,  have  dis- 
tinct bactericidal  values  though  less  than  the  phenols.  The  ses- 
quiterpene  alcohol  santalol  is  of  value  in  treatment  of  gonorrhea  but 
the  value  of  borneol  or  its  esters,  cineol,  menthol  and  the  like  in 
bronchial  infections  lies  more  in  the  stimulating  effect  of  these  sub- 
stances on  the  mucous  membranes  than  in  their  slight  bactericidal 
properties.  The  use  of  essential  oils  in  medicine  is  very  ancient  and 
though  many  of  the  prescriptions  of  the  old  herb  doctors  have  given 
way  to  carefully  prepared  and  standardized  extracts  or  to  new  syn- 
thetic drugs,  many  essential  oils  are  used  in  cosmetics,  and  a  few  have 
distinct  medicinal  values,  as  American  worm-seed  or  oil  of  cheno- 
podium,  the  active  constituent  of  which  is  ascaridol  (q.v.).  In  the 
treatment  of  persons  suffering  from  hookworm,  oil  of  chenopodium  is 
more  efficaceous  than  thymol;  both  are  about  equally  effective  in 
removing  necators,  but  oil  of  chenopodium  is  much  superior  to  thymol 
in  removing  the  more  resistant  species  of  hookworm.7  Essential  o;ls 
containing  the  ketone  thujone,  for  example,  the  volatile  oils  of  thuja, 
tansy,  sage  and  wormwood  (Artemisia  absinthium) ,  produce  character- 
istic disturbances  of  the  central  nervous  system  which,  in  the  case  of 
persons  addicted  to  the  drinking  of  the  liqueur  absinth,  results  in 
"rage  tanacetique." 

Considerable  difference  of  opinion  seems  to  exist  regarding  the 
physiological  properties  of  d,l.  and  d.l,  or  synthetic  camphor.  In 

•  "Anesthesia,"  698,  New  York,  1914. 

*  Report  of  Uncinariasis  Comm.  Rockefeller  Inst.,  N.  Y.,  1920. 


PHYSIOLOGICAL  AND  RELATED  PROPERTIES  595 

England  a  court  found  that  synthetic  camphor  possessed  properties 
identical  with  those  of  natural  camphor  (except  optical  rotation)  and 
therefore  ruled  that  its  use  in  pharmaceutical  preparations  was  per- 
missible.8 One  observer9  stated  that  he  could  detect  no  difference 
between  the  three  kinds  of  camphor,  by  peritoneal  injection,  and 
later  10  reaffirmed  that  all  three  varieties  are  equally  active.  Leyden 
and  Welden11  treated  frogs  with  chloral  hydrate  and  reduced  the 
heart  beat  to  7,  after  which  the  beat  was  raised  to  20  by  either  natural 
d.camphor  or  la?vo-camphor  but  state  that  synthetic  camphor  was 
without  action  on  the  heart.  Perkin's  epicamphor  was  found  to  have 
an  action  on  the  heart  slightly  less  than  natural  camphor.12  On  the 
other  hand,  Tsakalotos 13  states  that  synthetic  di.camphor  has  the 
same  heart  action,  also  using  frogs,  as  natural  camphor,  which  state- 
ment is  also  made  by  Lutz.14  Edsall  and  Means  15  investigated  the 
effect  of  natural  ^.camphor  on  respiratory  metabolism  but  their  results 
were  so  irregular  that  they  were  unable  to  draw  any  conclusion. 
Camphor  vapor  in  concentrations  of  one  to  two  parts  per  million  in 
air  is  sufficient  to  effect  the  heart  action  markedly.  [Heubner,  Z. 
ges.  exp.  Med.  I,  267  (1913).]  Natural  camphor  has,  however,  a 
pronounced  effect  on  the  muscular  respiratory  system.1.6  Heffter17 
states  that  there  is  no  apparent  reason  for  not  using  synthetic  cam- 
phor in  spirits  of  camphor  but  suggests  that  its  use  internally  be  not 
recommended  until  adequate  clinical  results  are  available. 

Sassen  18  used  cats  and  dogs  in  studying  the  physiological  proper- 
ties of  natural  and  artificial  camphor  and  states  that  with  these  ani- 
mals no  material  difference  could  be  noted  in  the  physiological  effects 
of  the  two  camphors.  For  both  natural  and  artificial  camphor  the 
fatal  dose  is  2  grams  per  1  kilo  weight  of  the  animal.  Doses  of 
0.025  to  0.05  gram  per  kilo  weight,  of  either  camphor  caused  a  per- 
ceptible increase  in  the  heart's  activity. 

The  United  States  and  German  Pharmacopoeias  prescribe  natural 
camphor.  Bruni 19  states  that  ^.camphor  is  about  13  times  as  toxic 
as  natural  d.camphor  and  Langgaard  and  Maass 20  state  that  the 

•  s  Pharm.  Zentr.  50,  563   (1909). 

Joachimoglu,  Arch  exp.  Path.  Pharm.  80,  1   (1916). 

0  Joachiinoglu,  ibid.,  80,  259,  282    (1917). 

1  Arch.  exp.  Path.  Pharm.  80,  24    (1916). 
2Bredt  &  Perkin,  J.  Chem.  Soc.  103,  2182    (1913). 
3J.  pharm.  chim.  17,  198    (1918). 

*Bcrl.  klin.   Wochenschr.  52,  322    (1915). 

8  Arch.  Inf.  Med.  U,  897   (1914). 

•Tsakalotos,  J.  pharm.  chim.   (7)   15,  19   (1917). 

7  Chem.  Abs.  9,  1970    (1915). 

"ScMmmel  &  Co.  Semi-Ann.  Rep.  1910  (2),  170. 

"Go**,  chim.  Ital.  38   (2),  1    (1908). 

*»Therap.  Monatsch.  20,  573    (1907). 


596      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

pharmacological  actions  of  the  two  forms  of  camphor  are  different 
but  in  their  paper  reference  is  made  to  trials  in  the  Charlottenburg 
hospital,  of  synthetic  and  natural  camphor  and  no  difference  was 
noted  between  the  two  when  used  internally  or  externally.  However, 
the  use  of  synthetic  camphor  for  internal  use  was  not  approved  dur- 
ing the  war  by  the  German  advisory  committee  on  medical  affairs. 
It  is  difficult  to  draw  any  definite  conclusion  from  these  contradictory 
findings  other  than  that  the  experimental  methods  employed  must,  in 
many  cases,  have  been  exceedingly  crude.  Borneol  produces  physio- 
logical effects  very  similar  to  camphor  but  less  pronounced,  which 
would  seem  to  indicate  that  the  oxidation  of  borneol  in  the  body 
is  not  rapid.  The  action  of  fenchone  is  very  similar  to  that  of  cam- 
phor.21 Camphoric  acid  has  the  same  antiseptic  properties  as  cam- 
phor, but  is  much  less  stimulating.  Large  doses  can  be  tolerated 
without  danger  and  it  has  been  recommended  for  bronchial  and  lung 
infections,  including  pneumonia,  but  clinical  results  are  not  yet  avail- 
able. Monobromocamphor  and  the  two  known  isomeric  monochloro- 
camphors  have  properties  not  differing  materially  from  camphor; 
these  halogen  derivatives  are  unusually  stable.  In  the  attempt  to  get 
the  same  physiological  action  of  camphor  more  promptly  by  means 
of  a  more  soluble  substance,  the  physiological  properties  of  oxy- 
camphor,  obtained  by  reduction  of  camphorquinone 

CO  CHOH 

C8H14<|  — ->    C8H14<| 

CO  CO 

was  tried,  but  this  substance  was  found  to  produce  effects  dia- 
metrically opposite  from  camphor;  whereas  camphor  stimulates  the 
central  nervous  system,  oxycamphor  depresses  excitation  of  the  re- 
spiratory center  and  is  accordingly  a  rapidly  acting  drug  in  dyspnoea.22 
Aminocamphor  and  bornylamine  retard  the  heart  action.  None  of 
the  numerous  derivatives  of  camphor  have  been  found  to  possess 
properties  on  the  whole  equal  to  camphor. 

The  anesthetic  action  of  a  large  number  of  volatile  chlorinated 
hydrocarbons  has  been  described.23  Ethyl  chloride,  butyl  chloride 
and  amyl  chloride  are  said  to  be  dangerous.  Carbon  tetrachloride  is 
very  slow  in  its  action  and  gives  a  prolonged  anesthesia  in  which  the 
convulsive  stage  is  apt  to  be  of  long  duration  and  acute.  It  is  also 

21  Arch.  eap.  Path.  Pharm.  50,  199    (1903). 

22  Cf.  Frankel,  Arzneimittel  Synthese,  Ed.   3,  1919,  p.  748. 

23  Cf.  Gwathmey,  Anesthesia,  1914 ;  Frankel,  Arzneimittel  Synthese,  E<3.  3,  1919. 


PHYSIOLOGICAL  AND  RELATED  PROPERTIES  597 

more  toxic  and  irritating  to  the  mucous  membranes  than  chloroform. 
Of  the  many  chlorine  derivatives  whose  anesthetic  action  has  been 
more  or  less  carefully  determined,  methyl  chloroform  CH3CC13,  and 
dichloroethylene  CHC1  =  CHC1,  appear  to  be  the  most  promising,24 
but  none  have  been  clearly  shown  to  be  as  satisfactory  as  chloroform, 
although  it  is  generally  recognized  that  it  would  be  desirable  to  dis- 
cover a  satisfactory  anesthetic  of  the  character  of  chloroform  but 
which  would  not  form  the  toxic  product  phosgene,  to  which  many  of 
the  fatalities  under  chloroform  anesthesia,  have  been  attributed. 

It  is  beyond  the  purpose  of  the  present  monograph  to  review  the 
whole  field  of  physiological  action  and  chemical  structure,  and  is  also 
foreign  to  the  author's  experience  in  research.  These  selected  notes 
are  therefore  included  which  seem  to  bear  upon  the  general  thesis  of 
the  present  volume. 

Diethyl  ketone,  C2H5CO.C2H5,  has  pronounced  soporific  properties 
and  has  been  recommended  25  as  an  inhalation  anesthetic  but  seems 
to  possess  no  particular  merit.  Cyclopentanone,  cyclohexanone  and 
cycloheptanone  also  have  pronounced  sleep  producing  power. 

Cyclohexylamine  and  n.hexylamine  have  practically  identical 
effects  upon  the  blood  pressure26  (normal  hexylamine  has  the  most 
pronounced  effect  of  any  of  the  normal  primary  amines). 

That  the  physiological  properties  of  comparatively  simple  deriva- 
tives of  the  aliphatic  hydrocarbons  are  very  imperfectly  known  has 
been  strikingly  demonstrated  during  the  recent  war  when  three  of 
the  war  poisons  of  greatest  value  proved  to  be  substances  of  this 
class.  The  physiological  properties  of  only  one  of  these  was  com- 
paratively well  known,  i.  e.,  phosgene.  Trichloromethyl  chlorofor- 
mate  and  mustard  gas  [|3,(3-dichloroethyl  sulfide]  were  very  imper- 
fectly known  before  the  war.  The  latter  substance  is  an  excellent 
illustration  of  the  fact  that  a  substance  may  have  a  very  mild,  sweet, 
rather  agreeable  odor  and  yet  be  exceedingly  irritating,  this  sub- 
stance killing  tissues  with  which  it  comes  in  contact  and,  within  a 
few  hours  after  exposure,  develops  most  painful  blisters.  Halogen 
derivatives  adjacent  to  a  carbonyl  group  are  exceedingly  irritating 
to  the  eyes  and  mucous  membranes,  as  illustrated  by  thje  lachrymatory 
"gases"  trichloromethyl  and  monochloromethyl  chloroformates, 
C1.C02CC13  and  C1.C02CH2C1,  acetone  derivatives  CH3COCH2Br, 
CH2C1.COCH2C1  and  the  like,  bromoacetic  ester  CH2Br.C02C2H5, 

**  Wittgenstein,  Arch.   exp.  Path.  Pharm.  83,  235    (1918). 

"Ann.  chim.  farmac.   1892,  124,  225. 

«» Cf.  Abelons  &  Bardier,  J.  phj/s.  1909,  34. 


598      CHEMISTRY  OF  THE  NON-BENZENOID  HYDROCARBONS 

bromo  acetophenone  C6H5COCH2Br  and  the  like.  A  case  of  deep 
destruction  of  the  tissues  was  described  by  Bogert 27  as  a  result  of 
brominating  in  acetic  anhydride.  The  tissues  were  killed  nearly  to 
the  bone,  under  unbroken  skin.  This  substance  would  seem  to  be 
more  destructive  to  the  deeper  tissues  than  mustard  gas  but  we  have 
no  data  as  to  effective  concentrations,  or,  in  fact,  the  identity  and 
nature  of  the  toxic  substance. 

"J.  Am.  Chem.  Soc.  29,  239    (1906). 


SUBJECT  INDEX 


Abietic  acid,  417,  418,  419 

Absorption  spectra,  of  hydrocarbons,  548, 

549 

Acetylene,  condensations  of,  35 
formation   from   ethylene,   35 
isopropyl,    212 
partial  hydrogenation,  161 
Acid  sludge,  nature  of,  131 
Acrolein.  reaction  with  bisulfite,  144 
Adsorption,     coloring    matter    from     oils, 

589 

gasoline  vapor  in  charcoal,  589 
selective — of  oils,   589 
Alcohols,    catalysts   for   dehydration,    155, 

156 

decomposition  to  olefines,  155 
ethyl,  from  coal  gas.  166,  167 
preparation  from  alkyl  sulfuric  esters, 

127,   128 

Aldehydes,    electrolytic    reduction    of,    50 
Alkyl* halides,   conversion   to  acetates,   74 
halides,  conversion      to      hydrocarbons, 

4.", 

halides.  dissociation   of,   72,   73 
halides,  preparation   of,   63,   65,  66 
halides.  reaction    with    alcoholic    alkali, 

73,   152 
halides,  reaction    with    alkali    formates, 

75 

halides.  reaction  with   aluminum  chlor- 
ide, 70 
halides,  reduction     by    hydriodic    acid, 

47 
halides.    reduction    by   metallic   couples, 

45.    48 
sulfates,    reaction    with    alcohol    alkali, 

74 

sulfuric  esters,  126,  127,  128 
sulfuric  esters  from  petroleum  refining, 

103.   106 

sulfuric  esters  in  refined  oils,  132 
Allene,   polymerization  of,  43 

dimethyl,   212,   224 
Allo-ociraene,  182 

Allyl  alcohol,  reaction  with  bisulfite,   143 
b'orneol,  from  camphor,  490 
bromide,   126 

halides,    conversion   to  ethers,    74 
Allylene,   physical   properties,  540,   548 
Aluminum    bromide,    action    on    hydrocar- 
bons,   45 

chloride,   action   on  hydrocarbons,  45 
chloride,  as  a  refining  agent.  109 
p.Amidobenzoic  acid,  hydrogenation,  283 
Amidocamphor,  484 

2-Amidocyclohexane  carboxylic  acid,  283 
Amines,    alicyclic,    reaction    with    nitrous 

acid.   525 

physiological  action   of,  597 
Aminocyclohexane,  290 
Amorphous  wax,  22 

Amyl  acetates,  from  chloropentanes,  74 
Amylene,   172 

anesthetic  action  of,  594 

autoxidation    of,    134 

conversion  to  amyl  methyl  ether,  131 

effect  in  synthetic  rubber,  217 

oxide,   223 

polymerization  by  fullers'  earth,  32,  43 


Amylene,   preparation   from   amyl  alcohol, 

173 

preparation  from  chloropentanes,  153 
preparation  from  n.hexane,  35 
preparation  by  pyrolysis  of  oils,  27,  36, 

37 

reaction   with    acetic   acid,    125 
reaction  with  aluminum   chloride,   45 
reaction  with   halogen  acids,  67,   127 
reaction   with   sulfur  dioxide.   144 
reaction  with  sulfuric  acid,  126.  131 

Amylenes,  rearrangements,  72,  150,  217 

Amylene.   solubility  in  aniline,  583 
solubility  in  liquid  SO2,  586 

Anesthesia,    by    inhalation    of    hydrocar- 
bons,  593.   594 

Aniline,   hydrogenation   of,   283 
reaction   with  ketones,   378 
solvent  for  hydrocarbons,  583 

Anthracene,    hydrogenation    of,    283,    284, 

Anthranilic   acid,   hydrogenation   of,   283 
Apocamphoric    acid.    442,    447 
Ascaridol,   constitution   of,  347,  348 

medicinal  value  of,  594 
Asphalt,  artificial,  52 

artificial,  effect  of  sulfur  on,  59,  60 

decomposition  of,  23 

formation  of.  32 
Autoxidation,  effect  of  light  on,  134 

of   unsaturated    hydrocarbons,    133 
Azelaic   acid,    conversion    to    cyclo-octane, 

520 

Azocamphor,  484 
Azulene,    549 


Baeyer's  stress  theory,   111,   112 

stress    theory    as    modified    by    Thorpe 

and  Ingold.  116,  117 
Beckmann     rearrangement     of     menthone 

oxime,   363 
Benzene,   absorption   spectrum  of,   549 

detection   in   and   isolation   from   petro- 
leum oils,  20 

distillation   with    n.hexane,   20 

in  oil  gas,  37 

hydrogenation   of,   242 

preparation  from  cyclohexane,  43,  44 
Benzocycloheptanone,    237 
Benzoic  acid,  hydrogenation  of,  282 
Benzylidene  menthone,  366 
Bertram  and  Wahlbaum  reaction,   125 
Bicyclohexane,   dimethyl,   249 
Bicyclononane,    243 
Bihydrolaurolactone,    475 
Bis-nitrosates,    146 
Bis-nitrosites,    146 
Bis-nitrosochlorides,    146 
Bisabolene,   314 
Blau   gas,    composition   of,   40 
Bleaching   of  mineral  oils.    52,   54 
Boiling    point,   effect   of    ring   closing    on, 
547 

relation   to  density,   542 

normal  and  cyclic  hydrocarbons,  547 

paraffines,  544 
Borneo  camphor,  494 
0-Borneol,  474,  475 


599 


600 


SUBJECT  INDEX 


Borneol,     cataljjtlc    (dehydrogenation    of. 
506 

conversion  to  camphene,  532,  534 

occurrence,    494 

oxidation  to  camphor,  505,  506 

physical   properties,   503 

physiological  action,  596 

preparation  from  bornyl  chloride,  502 

preparation    from    turpentine,   501,   502 

structure  of.  503 
Bornyl  chloride,  438,  440,   453,  494 

chloride,   conversion   to   camphene,   153, 
499 

chloride,  physical  properties,  497,  498 

chloride,    preparation    from    turpentine, 
496,   510 

chloride,    reaction   with    alkalies,    462 

chloride,  reaction  with  lime,  502 

chloride,  reaction  with  magnesium,  502 

chloride,    relation    to    fenchyl    chloride, 
508 

iodide,  438,  453 
Bornylene,   453 

hydrogenation,  463 

preparation     and     physical     properties, 
455,    456,    504 

reaction  with  diazoacetic  ester,  459 
Bornylene  carboxylic  acid,  455 
Bornylene  glycol,  486 
Bornylene-3-hydroxamic  acid,   474 
Bornyl    magnesium    chloride,    502 
Bromination   by  n.bromoacetamide,   123 
Bromocyclohexane,  Grignard  reactions  of, 

287 

Buchu  camphor,  371,  372 
Butadiene  caoutchouc,   211 

dimeride  of,  228 

physical    properties,    231 

preparation     from     acetaldehyde,     221, 
222 

preparation  from  acetone  oil,  221 

preparation  from  butyl  alcohol,  219 

preparation     from      butyric     aldehyde, 
221 

preparation   from  cyclohexane,   219 

preparation  from  hexane,   36 

preparation   from    petroleum,   42,   216 

dimethyl,   223,    226,    231 

dimethyl,    dimeride,    227 

dimethyl,     preparation    from    pinacone, 

156 
Butane,  chlorination  of,  87 

from  natural  gas,  14,  86 

synthesis,  48,  86 

vapor  pressure  of  liquid,  17,  85,  88 

2-bromo-3.3-dimethyl — ,   72 

2.2-diraethyl — ,   nitration  of,  61 

2-ethyl — ,  oxidation  of,  57 

2.2.3,3.-tetramethyl— ,   93 
Butanes,    chemical   properties    of,    172 

dichloro,  219 

physical  properties,  98 
Butene,  ozonide,  141 

Butene   (1)   2.3-dimethyl — ,  physical  prop- 
erties,   206 

3.3-dimethyl— ,   206 
Butene   (2),   preparation,  153 

2.3-dimethyl—,   206 
Butene   (3),  2.2.3.-trimethyl — ,  206 
Buetene    (4).  2.2.-dimethyl — ,   206 
Butenes,  physical  properties  of,  171 

preparation     from     butylalcohols,     150, 
156 

reaction       with       sulfur       dioxide, 
144 

reaction  with   sulfuric  acid,   126 
Butenes,  stereoisomeric  dibromo — ,  186 
n. Butyl    alcohol,    by    fermentation,    86 

alcohol,  for  rubber  synthesis,  219 
Butyl  alcohol,  tertiary,  70 

bromides,  preparation,  67 


Butyl   iodide,    tertiary,    reaction   with    sil- 
ver nitrate,  74 
glycol,   221 

Cadinene,  412,  413 

California   petroleum,   nitrogen   in,   29 

Caouprene   bromides,   211 

Camphane,   463,   464 

Camphanic  acid,  469,  481 

Camphene,   453 

acetylation  of,  510 

2-bromo-12-bromo — ,  465 

chlorohydrine,  124,  465 

conversion    to    isobornyl    acetate,    462, 
463 

glycol,   465 

hydrate,  444,   459,  502 

hydrochloride,   444,   459,   461,   462 

hydrogenation  of,  464 

impurities  in,  508 

molecular   refraction,    561 

nitrosite,   464,   465 

oxidation    products,   457 

ozonide,   139 

physical    properties,    454,    505 

preparation   from  borneol,   534 

preparation   from   bornyl   chloride,    153, 
510 

preparation,    industrial,    499,    500 

reaction  with   acetic  acid,  461 

reaction   with    bromine,   465 

reaction  with  diazoacetic  ester.   458 

reaction  with  formaldehyde,  465 

reaction  from  hydrogen  chloride,  462 

reaction  with  hypochlorous  acid,  465 
Camphenic   acid,   457,   458 
Camphenilane  aldehyde,  466 
Camphenilanic  acid,   466 
Camphenilol,    398,   466 
Camphenilone,  139,  456,  466 

conversion  to  santene,   398 

reaction       with       methyl       magnesium 

chloride,   460 
Camphenonic  acid,  458 
Camphocarbonic    acid,    487,    488 

conversion   to   bornylene,   504 
Campholactone,   475 
Campholide,    471,   474 
Campholytic  acid,   475,   476 

rearrangement  of,  482,  483 
Camphonanic  acid,  476 
Camphonene  series,  nomenclature  of,  475, 

476 
Camphonenic  acid,  475,  476 

constitution,  478,  479 
Camphonolic  acid,  480 
Camphonololactone,    476 
Camphononic   acid,   469 

constitution  of,  479,  480 
Camphor,   acid   addition   products  of,   467 

alkylation    of,    491 

"artificial,"    494 

benzylidene  compounds,  467 

Borneo,    494 

p.bromophenylhydrazone,  467 

buchu,   371,   372 

carvone-camphor,    377 

constitution,  467   et  seq. 

conversion  to  camphane,  463 

derivatives  of,   484 

derivatives  of,  physiological  action,  596 

glycol,    486 

hydrazone,  decomposition   of,   461 

identification   of,   467 

imide,   490 

impurities  in  synthetic,   507 

impurities  in  natural,  510 

natural,  466 

natural,    production   of,   492 

oxidation  products,  467  et  seq. 

oxime,  467,  484 


SUBJECT  INDEX 


601 


Camphor,  physical  properties,  466 

physiological   action,   594,   595 

preparation  from  borneols,  505 

preparation    from    camphoric   acid,    471 

quinone,    485 

quinone,    eight   oximino   derivatives    of, 
486 

reaction  with  mercuric  iodide,  467 

synthetic,   492   et   seq. 

synthetic,   purification  of,   509 

synthetic,   yields  of,  506.   510 

0-Camphor,  see  Epicamphor 
Camphoric  acid,  anhydride,  491 

conversion  to  camphor,  471 

iso.   472 

Komppa's   synthesis,   469,   470 

Perkin's   synthesis,   470,  471 

physiological  action.   596 

preparation  and  properties,  489 

preparation  from  bornylene,  456 

stereochemistry  of,  472 
Camphoric  acids,  nomenclature  of,  477 
Camphoronic  acid,  468,  469,  482 
Camphoroxalic  acid.  489 
Camphorphorone,  370 

conversion  to  l-methyl-3-isopropylcyclo- 
pentane,  490 

preparation   and  properties,  489,  490 
Camphyl   glycol.   488 
Cantharene,  310 
Carane.  from  pulegone,  241,  372 

physical   properties,   553 
Carbides,  formation  from  methane,  79 
Carbon    black,    yield    from    natural    gas, 

Carbon,   colloidal,   in  oils,   105 

Carbon    tetrachloride,    from   methane,    79, 

80 

Carburetted  water  gas,  composition,  40 
Carbyl  sulfate,   143 
Carene,  403 
Carone,  384 
Caronic  acids,   synthesis.   248,   386 

cis  and  trans,  117,  385 
Carvenene,    340 
Carvenone.   339 
Carveol.  356 
Carvestrene,   384 

Carvomenthene,  from  limonene,  318 
Carvomenthol,   356 
Carvomenthone.    chlorination    of,    365 

rearrangement   of,   527,   528 
Carvone,   318 
Carvone-anil,  378 
Carvone  camphor.  377 

constitution,  327,  328,  356 

conversion    to    2-methylcymene,    376 

conversion  to  eucarvohe,  373,  517 

conversion  to  sylvestrene,  384 

hydrogenation   of,   374 

isomerization  by  sunlight,  377 

occurrence.    375 

oxidation  of,  328 

preparation  from  pinene,  431.   432 

preparation  from  a-terpineol,  329 

reaction   with  aniline,   378 

reaction  with   hydrogen   cyanide.   378 

reaction  with  hydrogen  sulfide,  375 

reactions  of.  375 
Carvotanacetone,  356,  375 

from  a-phellandrene,  380 
Carvoxime,  317,  327 

conversion   to  amidothymol,   375 

hydrogenation,    375 
Caryophellene,   409.   410,  411 
0-Caryophellene,  411 
7/m-Caryophellene,   412 
terp-Caryophellene,  412 
Castor  oil,  solubility  in  hydrocarbon  oils, 
582 


Cedrene,   416 

Cedrone,   416 

Ceresine,  18,  22,  96 

Chlorinated     hydrocarbons,     physiological 

action  of,  596,  597 
Chlorine,    substitution,    effect    on    melting 

point,  545 
Chlorocosane,   102 
Chlorohydrines.   123,   124 
Cholesterol,    205,    522 

decomposition   products,    31 
decomposition      products,      optical      ac- 
tivity,  565,   566 
Cholesterylene,    205 
1.4-Cineol,   336 

physical   properties,   347 
1.4-Cineolic  acid,  348 
1.8-Cineol,    336 

addition  products,  345 
conversion  to  terpin-diacetate,  345 
isolation   of,   347 
ketone  derivative.  347 
occurrence  and  properties,  344,  346 
oxidation,  346 
1.8-Cineol.   meta,  389 
1.8-Cineolic   acid,   346 
Citral.  chemical  properties,  200 
constitution.  185 
conversion  to  decane,  199 
conversion  to  ionones,  200,  201 
hydrogenation,   199 
hydrolytic  decomposition,  184 
physical  properties,  197 
reaction  with  alkyl  magnesium  halides, 

204 

reaction  with  ethyl  acetoacetate,  204 
reaction  with  j8-naphthylamine.  200 
reaction  with  sodium  bisulfite,  144,  145, 

198,   199 

relation   to  geraniol  and  nerol,  186 
stereochemistry   of,   186 
Citronellal,  constitution  of,  189 
conversion  to  isopulegol.  192,  238 
reaction  with  bisulfite,  145 
Citronellic   acid,   190 
Citronellol,  constitution  of,  189 
physical  properties,  197 
relation  to  rhodinol,   190,  191 
stability  of,   194 
Coal,    carbonization   at   low  temperatures. 

23,   34,   41 

hydrogenation   of,   284 
Coal  gas.  composition  of,  40 
Cocain,   decomposition    products.   512 
Color,  of  hydrocarbons,  548,  549 
Coloring  matter,   of  petroleum  distillates, 

104 

Conylene.    179 
Copaene,   417 
Crithmene,    340.    341 

Critical   pressures,   of   hydrocarbons.   548 
Critical     temperatures    of    hydrocarbons, 

548 
Crotonic  aldehyde,  reaction  with  bisulfite, 

144 
Cvclic    hydrocarbons,    viscosities    of,    577. 

578 

Cyclic  structures,  relative  ease  of  forma- 
tion, 116 
Cyclobutane,    angle    of    strain     (Baeyer), 

carboxylic  acid,   235,   251,    257 
derivatives,    comparison    with    n.butane 

derivatives,  251,  247 
derivatives,    molecular   refraction,    555 
1.2-dibromo— ,  252 
1.1-dicarboxylic  acid,  256 
1.3-dicarboxylic  acid.  257 
1.2-di-isopropyl — ,   256 
1.2-di-isopropylidene — ,  256 


602 


SUBJECT  INDEX 


Cyclobutane,    l.l-dimethyl-2-methylene-3- 
isopropyl — ,  256 

ethyl — ,   115,   255 

methene — ,    253 

methyl,   234,   254 

nitromethyl,   525 

preparation  and  properties,  251 

preparation   by   polymerization,    212 

stability   of  the  — ring,   114,   252,   429, 
430,   433 

1.1.3.3-tetramethyl-2.4-diethyl— ,  115 

1.1.2.2-tetracarboxylic  acid,  257 

1.1.2-trirnethyl-3-isopropyl — ,  256 
Cyclobutanol,    251 
Cyclobutanone,   255 

2-isopropylidene — .,  256 

2-isopropyl,    256 
Cyclobutene,  bromination  of,  255 

from    cyclobutylamine,   252 

synthesis,  156 
Cyclobutylamine,     reaction     with     nitrous 

acid,  525 

Cyclobutylcarbinol,    conversion    to    cyclo- 
pentyl   bromide,   524 

dimethyl — ,  rearrangement,  524 
Cyclobutylemethylamine,      conversion      to 

cyclopentanol,  525 
Cyclobutylmethyl  carbinol,   255 
Cyclocamphane,   464 
Cyclocamphanol,  464 
Cyclocamphanone,  464 
Cyclocampholenic  acid,   464 
A*-Cyclocitral,   202 
Cyclofenchene,  439 
Cyclogeraniolene,   180 
Ai-s-Cycloheptadiene,  511,   512,  513 
Cycloheptane,    angle    of    strain    (Baeyer), 
114 

from  cyclohexanes,  530 

from  petroleum,  24 

preparation  and  properties,  511     ' 

1.2-dibromo — ,    512 

1.2-dimethyl-1.2-dihydroxy,    239 

methene,   516 

1.2.4-tricarboxylic  acid,   515 
Cycloheptanol,   511 

1-methyl,  516 

acetic   acid,   516 
Cycloheptanone,  233,  515 

bromination,  516 
Cycloheptatriene,  dimethyl,  from  p.xylene, 

514 

Cycloheptatrienes,    preparation,    514 
Ai-a-s-Cycloheptatriene,    511,    513 
A2-5-T-Cycloheptatriene,  2.5-diinethyl-7-car- 

boxylic   acid,    514 
Cycloheptene,    511,    512 
A^Cycloheptene  methyl,  516 
Ai-Cycloheptenone(3),-2    methyl,    516 
Cyclohexadienes,       absorption       spectrum, 
o49 

preparation   and   properties,    291 

reaction  with  sulfuric  acid,  293 
Ai-3-Cyclohexadiene,    291,   292,   557 

1.3-dimethyl.  238 
A^-Cyclohexadiene,    291 

1.4-di-isopropenyl,  309 
Cyclohexane,  24,  38,  280,  285 

Baeyer's   synthesis,    234 

bromination,  286 

chlorination,  288,  289 

conversion    to   benzene,    34,   43,   282 

conversion    to   cyclopentanes,    368 

conversion  to  methylcyclopentane,  524 

critical   temperature  and   pressure,   548 

cryoscopic    solvent,    583 

dehydrogenation,   43,   44,   282 

derivatives,   stereochemistry,  279 

detection  of,  2S2 

effect  of  ring  closing  on  molecular  re- 
fraction, 556,  557 


Cyclohexane,  halogenation,  64 

identification  of  alkyl  derivatives,  303 

isolation    from    petroleum,    18 

metal  derivatives,  287 

nitration,   289 

preparation,  234,  235,  242,  280,  283 

pyrolysis  of,   36,   285 

separation      from     methyl-cyclopentane, 

43 
Cyclohexane,   ethylidene,   308 

hexacarboxylic  acid,   281 

hexol,  294 

iodo,  289   ' 

methene,   298,    299 

methyl,   296,   297 

methyl,   chlorine  derivatives,  297 

methyl,  nitration   of,   289 

methyl,   1.1-nitro,  297 

methyl,  1.3-nitro,  297 

methyl,  reaction  with  sulfur,  59 

pentol,   294 


phenyl,   nitration   of,   611 
solubility  in  liquid   SO2,  586 


tetrachloro — ,  289 

trichloro-,    122 

Cyclohexanes,    alkyl,    conversion    to    ben- 
zene  derivatives,    303 

alkyl     derivatives,     table     of     physical 
properties,   301,   303 

amino,    283,   290 

bromo,    conversion    to    cyclohexanol,    75 

carboxylic   acid,   235,   282 

carboxylic   acid,   4-amido,    283 

1.1-diacetic   acid,    117 

diamino,    290 

1.2-dicarboxylic  acid,   282 

1.3-dicarboxylic   acid,   236 

1.4-dicarboxylic   acid,   279 

dichloro,  219 

1.4-di-isopropyl— ,  308 

dimethyl—,  243 

1.1-dimethyl — ,  300 

1.2-diol,    294 

1.3-diol,  294 

1.4-diol,  234 

1.4-dione,  233,  280 

1.3-diones,  280 
Cyclohexanol,  decomposition   of,   288 

preparation  and  properties,   75,   293 
Cyclohexanol  ( 1 )  ,-2.2-dimethyl,   533 

-1-methyl,   298,   299 

-1-methyl,   oxidation   of,   254 
Cyclohexanols,     table     of     physical     prop- 
erties, 295 
Cyclohexanone,    233,   234,   296 

-4-carboxylic   acid,   321 

chlorination  of,   64 

conversion  to  cyclopentanones,  116,  370, 
371 

dimethyl,     from      tetrahydro-eucarvone, 
517,   518 

preparation  from  nitrocyclohexane,  289 

4-propyl — ,  one (3),  367 

reaction   with   bromoacetic  ester,  298 

reduction  to  cyclohexanol,  285 
Cyclohexene,    absorption    spectrum,   549 
'  catalysis   of   autoxidation,   134 

conversion  to  butadiene,  217,  218 

ozonide,   142 

preparation   and   properties,   288 

preparation     from     amino-cyclohexanes, 
290 

preparation    from    cyclopenthylcarbinol, 
526 

reaction  with  acetyl  chloride,  121 
Cyclohexenes,  table  of  physical  properties, 

305 

A^Cyclohexene  aldehyde,  299 
A2-Cyclohexene  carboxylic  acid,  282 
A^Cyclohexene-l-methyl^-carboxylic    acid, 
321 


SUBJECT  INDEX 


A3-Cyclohexene-l-methyl-4-carboxylic    acid, 

332 

As-Cyelohexene-l.l-dimethyl,  300 
Ai-Cyclohexene-1.2-dimethyl,  307,  536 
A3-Cyclohexene-1.3-dimethyl,  238 
A^Cyclohexene-l^-dimethyM-isopropyl, 

Ot>3 

A8-Cyelobexene  1.3-dimethyl-3-ethenyl,  228 
A*-Cyclohexene-l-ethenyl,  228 
A»-Cyclohexene,  methyl,  299 
Cyclohexenes,  methyl — ,   preparation,  297, 

298 

Cyclohexyl  aldehyde,  299 
Cyclohexylmenthene,  360 
Cyelohexylmethylamine,  conversion  to  cy- 

clopentanol,  525 
Cyclohexylnitromethane,  297 
Cyclo-isocamphoronic  acid,   464 
Cyclo-octane,  519,  520 
Cyclo-octadiene,  A1-3,  520 

A*-*,   520 

A*-",    520 

A1-*,  ozonide  of,  140 

A»-«,  -3-4-dimethyl,  520 
Cyclo-octatetrene,  521 

molecular  refraction,   560 
Cyclononane,   521 
Cyclopentadiene,  bromination  of,  260 

dimeride,  260 

preparation,  260 

reactivity  of  the  CH2  group,  261 

reaction  with  ketones,  261 

reaction  with  sulfuric  acid,  261 

4-methyl-2-ethyl,   261,   262 
Cyclopentane,  38,  258 

angle  of  strain    (Baeyer),   114 

dehydrogenation  of,  43 

relative  ease  of  formation,  116,  240 

1.2-diearboxylic  acid,  276 

dimethyl,  38 

dimethyl,  from  cycloheptyl-iodide,  524 

1.1-dimethyl,  270 

1.2-dimethyl,   271 

1.3-dimethyl,  272 

1.2-dimethyl-3-isopropyl,   272 

ethylidene,  266 

isopropylidene,   267 

methene,   265,  266 

methyl,  262 

methyl  from  benzene,  258 

methyl  from  cyclohexane,  36 

methyl  from  cyclohexanol,  258 

methyl  petroleum,  24,  38 

l-methyl-2-carboxylic  acid,  275 

methyl,  nitro  derivatives,  262,  263 

l-methyl-2.3-dicarboxylic  acid,  277 

l-methyl-3-ethyl,  272 

l-methyl-2-isopropyl,   272 

l-methyl-3-isopropyl,  490 

l-methyl-3-methene,  269 

l-methyl-2-nitro,  262 

1.2.4-tricarboxylic  acid,   277 

1.1.3-trimethyl,   408 

sulflnic  acid,  75 

sulfonic  acid,  259 
Cyclopentanol,   259 

from  cyclobutyl-methyl  amine,  525 

(l),-l-methyl,   236 

(2),-l-methyl,    262 
Cyclopentanone,  233,  267 

conversion  to  amidocapronic  acid,  270 
Cyclopentanone,  enolization  of,  264 

preparation,  116,  239,  264 

preparation  from   cyclohexanone,   370 

preparation  from  1.3-dibromo-cyclohexa- 
none,  536 

reaction  with  aldehydes,  265 

reaction  with  alkyl  magnesium  halides, 
266 


Cyclopentanone,  reaction  with  bromoacetic 
ester,  267 

reaction  with  formic  acid,  265 

2.5-dimethyl,  264 

2-ethyl,  264 

isopropylidene,    265 

2-methyl,    262,    268 

3-methyl,  268,   269 

Cyclopentanone   (2),  1  methyl-3-isopropyl, 
370 

sulfonal,   265 
Cyclopentene,  cyclopentyl,  267 

dicyclopentyl,  268 

iodohydrine,  276 

oxide,   276 

ozonide,  141 

preparation  and  properties,  259 
A2  Cyclopentene,  1.1-diethyl,  524 
A»  Cyclopentene,  1.2-diethyl-,  116,  524 
A*  Cyclopentene,   1.2-dimethyl,  271 
A*  Cyclopentene,  1.1-dimethyl,  270,  271 
AI  Cyclopentene,isopropyl,  267,  533,  534 
A*  Cyclopentene,2-methyl.  269 
Cyclopentenes,    table    of    physical    proper- 
ties,  274 
Cyclopentyl  carbinol,  526 

methylamine,  525 
Cyclopropane,    234,    247 

angle   of    strain    (Baeyer),    114 

derivatives,  Kishner's  synthesis,  241 

derivatives,  molecular  refraction,  553 

derivatives,   synthesis  by  diazomethane, 
239,   242 

preparation   and   properties,   247 

ring  as  intermediate  in  rearrangements, 
71,  526 

ring  in  tricyclene,  444 

ring  rupture  in  sabinane,  526 

ring  rupture  in   thujone,   400.  401 

ring,  stability  of,  67,  114,  245,  246 
Cvclopropane,  dicarboxylic  acid,  235 
.1-dimethyl,   247,   248 
.2-dimethyl,   114,   248 
.l-dimethyl-2-carboxylic  acid,  115 
.l-dimethyl-2-isobutenyl,   115,  241,  250 

ethyl,  254 

methyl,  247 

-methyl-1.2-diethyl,   249 
-methyl-2-isobutyl.  249,  409 

methylisopropyl,    241.   249 

methyl,   1.2.3-tricarboxylic  acid,   434 

nitro  derivatives,  247 

phenyl,  241 

1.2.3-tricarboxylic  acid.    459 

1.1.2-trimethyl,  114.  248 

1.2.3-trimethyl,  248 
Cyclopropyl  ethyl  ketone,   246 

methyl  ketone,  236 
pp-Cymene,  hydrogenation  of,  243 

Deblooming  reagents,  105 
Decadienes,  181 
Decahydronaphthalene,  242 

in  petroleum,  24 
n.Decane,  99 
Decanes,  94,   99 
Decatrienes,  181 

Decene,  from  undecylenic  acid,  151 
Decene(l),   207 

reaction  with  benzoyl  peroxide,  135 
Decolorizing  of  petroleum  oils,  105 
Dehydrocamphoric  acid,  476 
Dehydrogenation,  43 
Demethylated   pinone,    233 
Density,  relation  to  boiling  point,   542 

relation  to  molecular  volume,  538,  540 
Desulfurizing  of  petroleum  oils,  28 
Diallyl,  polymerization  of,  43 
Diaminocyclohexanes,    290 


604 


SUBJECT  INDEX 


Dibromocyclic      ketones,      rearrangement, 

o27,    528 

Dicamphyl  ethane,  489 
Dichlorocyclohexanes,  289 
Dichloroethylene,  as  an  anesthetic,  597 
&3-Dichloroethyl  sulfide,   164 

physiological  action,  597 
Dichloropropyl  sulfide,   170 
Dicyclobutane,  derivatives  of    250 
Dicyclohexane,   2.6.6-trimethyl    409 
Dicyclohexylamine,  283 
aa-Dicyclohexylethane,  405 
Dicyclohexylpropane,   243 
Dielectric  constants,  97,  576 
Dienes,  absorption  spectra  of,  549 
conjugated,  heats  of  combustion,  572 
conjugated,   odor  of,   591 
conjugated,  polymerization,  212 
conjugated,     physical     properties,     231, 

292,    5o6 
conjugated,  reaction  with  sulfuric  acid, 

132 

conjugated,  refractive  index,  292    556 
Diethylene  oxide,  342 
Dihydrocamphorphorone,  371 
Dihydrocarveol,  129,  327,  355,  356 
Dihydrocarvone,  356 
Dihydrocedrene,    416 
Dihydrocitral   (see  Citronellal) 
Dihydrocuminaldehyde,  381 
Dihydroeucarvone,  374,  518 
Dihydrolinalool,  196 
Dihydrolimonene,  48 
Dihydromyrcene,  181,  196 
Dihydroperillic   alcohol,   379 
Dihydropinolone,  350 
Dihydrosylverterpineol,  391 
Di-isobutene,  oxidation  of,  135 
Di-isobutyl,  92 
Di-isoprene,   227 
Di-isopropyl,    nitration    of,    61 

critical  constants,  548 
p-Diketocamphane,  486,  487 
2.2-Dimethyl-l-chloropropane,      rearrange- 
ment of,  463 

3.3-Dimethyl- (0.1.3  )-dicyclohexane,    408 
Dimethyl  granatinine,  519 
Dimethyl  norcampholide,  456 
Diosphenol,  372,  373 
Dipentene  (see  also  Limonene) 

dihydrochloride,  507 

occurrence,  315 

physical  properties,  317 

pyrolysis  of,  216 

synthesis  of,   321,   323 
Diphenylamine,  hydrogenation  of,  283 
Dispersion,   molecular,   562 

molecular  effect  of  ring  closing,  554 
n.Docosane,  100 
n.Dodecane,   99 

Dodecene(l),  physical  properties,  208 
Dotriacontane,  19,  101 
Drying   oils,   polymerization  of,   213 
Dutch  liquid,   165 

Edeleanu,  method  of  oil  refining,  109    144 

586 

n.Eicosane,   100 
Emulsions,  587,  588 
Epiborneol,  474,  475 
Epicamphor,   473,   474,   475 
Essential  oils,  paraffines  in,  95,  96 
Ethane,  82  et  scq. 

chlorination,    84 

occurrence  in  natural  gas,  13,  14,  83 

oxidation,  57 

physical  properties,  17,  83,  540,  548 

preparation  from  ethylene,  35 


Ethane,  preparation  from  sodium  acetate, 

50 

reaction  with  ozone,   142 
separation  from  methane,  83 
vapor  pressure  of  liquid,  17,  83,  84 
Ethanol  mercury   salts,   168 
Ether  formation,  from  alkyl  halides,  73 
Ethylene,   compounds  with  metallic   salts, 

Io9 

compressibility,  159 
conversion   to   acetylene,   35 
decomposition  by  heat,  33,  35,  160 
heat  of  combustion,  571,  575 
hydrogenation  to  ethane,  36,  48 
oxidation  to  formaldehyde,   162 
percent  in  oil  gas,  40 
physical  properties,  84,  158,  540,  548 
polymerization,  211 
preparation,   125,   155,   160,   161 
preparation  from  ethyl  chloride,  73,  153 
reaction  with  benzoyl  chloride,  165 
reaction  with  boron  trifluoride,  166 
reaction  with  bromine,  165 
reaction  with  chlorine,  165 
reaction  with  iodine,  166 
reaction  with  mercury  salts,  168,  169 
reaction  with  nitrosyl  chloride,  146 
reaction  with  ozone,  137 
reaction  with  phosgene,  165 
reaction  with  selenium  chloride,  164 
reaction  with  sulfur  chloride,  164 
reaction  with  sulfuric  acid,  166 
reaction  with  sulfur  trioxide,  143 
separation   by  mercury   salts,   169 
solubility,    158,    160,    583 
solvent  power  of  compressed,  583 
vapor  pressures  of  liquid,  84 
Ethylenes,    effect    of    substituents    on    ad- 
dition  of  bromine,   120,  121 
substituted,  nitration  of,  122 
substituted,  polymerization,  122,  211 
Ethylene  bond,   absorption  spectrum,   548, 

549 

bond,  addition  of  water,  125 
bond,  angle  of  strain   (Baeyer),  114 
bond,    chemical    properties    as    modified 

by  substituents,  122  et  seq. 
bond,   conjugated,  mol.  refraction,   556 
bond,    heats    of    combustion    of    hydro- 
carbons containing,   572 
bond,  hydration  by  organic  acids,  125 
bond,  hydration  by  sulfuric  acid,  126 
bond,   hydrolytic  rupture  by  alkali,  149 
bond,  molecular  compounds  with,  120 
bond,  nature  of,  111 
bond,  reaction  in  presence  of  aluminum 

chloride,  121 
bond,    reaction    with    acetoacetic    ester, 

149 

bond,  reaction  with  amines,   147,  148 
bond,   reaction  with  bromine,   120,  121, 

bond,    reaction    with    hydrocyanic   acid, 

bond,    reaction    with    hydrogen    sulfide, 

148 
bond,   reaction  with  hypochlorous  acid, 

123 

bond,  reaction  with  iodine,  123 
bond,    reaction    with    metallic    sodium, 

149 
bond,    reaction    with    nitrosyl    chloride, 

145 

bond,    reaction   with  organic  acids,   125 
bond,    reaction    with   organic  peroxides, 

Io4,    13o 

bond,  reaction  with  ozone,  137  et  scq. 
bond,  reaction  with  permanganate,   135 
bond,  reaction  with  sulfur,  135 


SUBJECT  INDEX 


605 


Ethylene  bond,  reaction  with  sulfuric  acid, 

126 

bond,  reaction  with  sulfurous  acid,  144 
bond,  reaction  with  sulfur  trioxide,  143 

Ethylene  bonds,  refractivity  of  conjugated, 

OOD 

bonds,   refractivity  of  semi  cyclic,   560, 
561 

bonds,  rupture  by  air  oxidation,   134 

bonds,  thermochemistry  of,  575,  576 

bonds,  type  reactions  of,  119 
Ethylene    bromide,    reaction    with    silver' 

nitrate,   74 
Ethylene  bromohydrine,  163 

chloride,  165 

chloride,   conversion  to  glycol,   75 

ehlorobromide,    166 

chlorphydrine,  163 

diamine,   147 

oxide,  constitution  of  Thomsen,  569 

oxide,  preparation,  341,  343 

oxide,    derivatives,    in    rearrangements, 

531 

Ethyl  chloride,  conversion  to  ethylene,  73 
Ethyl  hydrogen  sulfate,  hydrolysis  of,  127 
2-Ethyl-p-menthanone,    360 
2-Ethyl-menthol,  360 
Eucalyptus  oils,  346,  415 

parafflnes  in,   19 
Eucarvone,  373,  519 

constitution,   517 
Eudesmene,  415 

Fatty    acids,    decomposition    to    hydrocar- 
bons, 33 

oxidation  of,   58 

from  paraffine,  52,  55,  56 

from  oleh'nes  by  ozone,  57,  143 

reduction  to  hydrocarbons,  47,  50 

salts,  electrolysis  of,  50 
Fatty  oils,  polymerization  of,  213 
Fenchane,  452 
a-Fenchene,  446,  448,  451 
0-Fenchene,  146,  448 
7-Fenchene,  449 
5-Fenchene,  448 

Fenchenes  in  camphene,  507,  508,  509 
Fenchenonic   acid,   442 
Fenchocamphorone,  447 
Fencholic  acid,  451 
Fenchone,  physical  properties,  446,  447 

synthesis,  449 

in  synthetic  camphor,  507 

and     isofenchone,     relation    to     fenchyl 

alcohols  and  tricyclene,  509 
Fenchosantenone,  450 
Fenchyl  alcohol,  440,  441 

alcohol,  dehydration  of,  451 

alcohol,  from  pinene,  501,  507 

chloride,    reactions   of,    451 

chloride,    relation    to    bornyl    chloride, 

508 

Fish  liver  oils,  205 

Fish  oil,  distillation  under  pressure,  31 
Formaldehyde,      from      hydrocarbons      by 
partial  oxidation,  57 

from  ethylene,  162 

from  methane,  78 
Formolite  reactions,  286,  287 
Formylmenthylamines,   364 
Fluorenone,  reduction  of,  530 
Fluorescence,  of  hydrocarbons,  549,  550 

of  petroleum  distillates,  105,  550 
Friedel  and  Craft's  reaction,  for  ring  clos- 
ing, 45,  237 

Fullers'    earth,   filtration   of  oils  through, 
589 

polymerization  by,   32,  43 

as  a  refining  agent,  110 


Fulvenes,  261 

absorption  spectra,  549 
Fusel  oil,  220 

Gas,  coal,   33 

natural,   analysis  by  fractional  distilla- 
tion,  14 

natural,  composition,  13,  14 

natural,  fuel  value  of,  14,  15 

natural,   origin  of,   19 

Pintsch,  37 

Gases,   composition   of  various  industrial, 
40 

solvent  power  of  compressed,  583 
Gasoline,  electrostatic  charges,  576 

hydrocarbons  in,  24 

oxidation  by  air,  133 

properties  of  highly  "cracked,"  42,  43 

refining  of,  102,  109,  110,  131,  132 

removal  from  natural  gas,  14,  16 

temperatures  for  producing  by  pyrolysis, 

36 
Geraniol,  conversion  to  dipentene,  187 

conversion  to  linalool,  188 

occurrence,  192,  193 

odors,  204 

oxidation,  188 

oxides,   194 

physical  properties,  187 

reaction  with  bisulfite,  196 

relation   to   citral   "a,"    186 

stability  of,  194 
Geraniolene,  180 
Geranyl  acetone,   193 

chloride,   193 

Glycerine,  synthesis  from  propylene,  86 
Glycols,  as  products  of  oxidation,  135 

preparation  from  oxides,  342 
Greases,  calcium  soaps  in,  587 
Grignard  reactions,  for  hydrocarbons,  46, 
47,   75 

reactions,  for  ring  closing,  234,  236 

reactions,  on  carvone,  376,   377 

Haber's  methane  whistle,  77 
Hall   refining  process,   110 
Haller's  reactions,  on  camphor,  491 

reactions,  on  menthone,  360 
Heats  of  combustion,   benzene  and   cyclo- 
hexenes,  574 

CH2  ;n  paraffine  series,  574 

cyclic  hydrocarbons,   573 

effect    of   conjugation   of   double   bonds, 
572 

— in  paraffine  hydrocarbons,  575 

hydrocarbons,  table,  571 

isomeric  substances,  571,  572 

unsaturated   hydrocarbons,   575,   576 
Heats    of    dissociation    of    C-C    and    C-H 

bonds,  574,  575 
n.Heneicosane,   100 
n.Hentriacontane,  in  natural  waxes,  19 

physical   properties,    101 
n.Heptacosane,  in  beeswax,  19 

physical  properties,   101 
Heptadiene  A*«,  232 

A^-3.5-dimethyl,   232 

A3'«-3-methyl,  232 

A^-6-methyl,  232 
n.Heptadecane,  100 
Heptadecene,  from  oleic  acid,  151 
Heptane,  bromination,  64 
n. Heptane,  critical  constants,  548 

occurrence,   18,   19,   20 

physical  properties,  99 

preparation  from  cycloheptane,  511 

pyrolysis  of,  36 

sulfonation  of,  63 


606 


SUBJECT  INDEX 


n. Heptane,  vapor  pressures  of,  17 

2,6-dimethyl,  nitration  of,  60 

2,6-dione,  215 

2-methyl,   91 

3-methyl,    91 

4-methyl,   92 
Heptanes,  89,  91 
Heptatriene,  A'  -8  -5,  232 
Heptene(l),   206 

-6-methyl,  207 
Hepteue(2),   206 

-2-methyl,  207 
Heptene(3),    preparation,    152 

-2-methyl,  207 
Heptene  ( 4 )  ,-4-methyl,  207 

3.3.5-trimethyl,    208 
Heptene(5)-2-methyl-5-ethyl,  208 
n.Heptyl   aldehyde,   90 
n.Hexacontane,  51 
n.Hexacosane,  101 
n.Hexadecane.    100 
Hexadecene,  208 

Hexadiene,  Al!*-2.5-dimethyl,  ozonide,  140 
ozonide  of,  140 


-2.5-dimethyl,  179 
,  heat  of  combustion,  576 
,  physical  properties,  232 
-3.5-dimethyl,  232 
3-methyl,  232 


A3-M-methyl,   232 
n.Hexane  and  benzene,   distillation  of,  20 

critical  constants,   548 

dehydrogenation,  43,  44 

oxidation,   57,   58 

in  petroleum,  18,  20 

physical  properties,  99,  548 

pyrolysis  of,   36,   150 

reaction  with   sulfur,   59 

solubility   of   sulfur  in,    583 

sulfonation  of,   63 

synthesis  of,  46 

vapor  pressures,  17 

-2-butyl,  oxidation  of,  57 

-2.4-dimethyl,   92 

-2.5-dimethyl,   92 

-3.4-dimethyl,   93 

Iso,  in  petroleum,  20 

iso,  physical   properties,    99 
Hexanes,  89 

molecular  volume  of,  539 
n.Hexatriacontane,  101 
Hexatriene  A»  •«  •»,  232 
Hexene(l),  preparation,   151,   152 

physical   properties,   206 

-3-methyl,   206 

Hexene(2),  hydrogenation  of,  48 
Hexene(4),  -2-5-dimethyl-4-isobutyl,  208 

-4-methyl,  206 
Hexenes,   in  petroleum  distillates,   27 

reaction  with  sulfuric  acid,  107 
Homo-apocamphoric  acid,  447 
Homocamphor,  491 
Homocamphoric  acid,  471 
Homomenthene,  366,  367 
Homoterpenylic  acid,  325,  326 
Homo-a-terpinol,  353 
Hydrocamphorylacetic  acid,  491 
Hydrocarbons,  benzenoid,  from  oil  gas,  37 

benzenoid,  in  petroleum,  26,  38 

benzenoid,   from  petroleum,   36 

cyclic,   table   of  physical  properties,   25 

optically  active,  in  oils,  50 

oxidation  by  nitric  acid,   57 
oxidation  of  saturated,  52,  57 

oxidation  by  permanganate,  57 

paraffine,    table    of   physical   properties, 
21,  206 

synthesis  of  optically  active,  564 


Hydrocarbons,  unsaturated,  analytical  de- 
termination, 132 

unsaturated,  conversion  to  alcohols,  106 

unsaturated,   determination   of  constitu- 
tion, 131,  135,  150 

unsaturated,  effect  of  heat  and  pressure, 
42 

unsaturated,  occurrence  in  petroleum,  27 

unsaturated,   odor  of,   103 

unsaturated,  oxidation  of,  133,  135 

unsaturated,     and     petroleum     refining, 
131 

unsaturated,  polymerization,  210  et  seq. 

unsaturated,  preparation  of,  150  et  aeq. 

unsaturated,       preparation       of       from 
amines,  156,  290 

unsaturated,    preparation    by    Grignard 
reaction,  152,  156 

unsaturated,    preparation    from    methyl 
xanthogenates,   154 

unsaturated,   preparation  from   palmitic 
esters,  154 

unsaturated,    preparation    by    pyrolysis, 
157 

unsaturated,    reaction    with    aluminum 
chloride,  45 

unsaturated,  reaction  with  fullers'  earth, 
32,  43 

unsaturated,      reaction      with      nitrosyl 
chloride,   146 

unsaturated,  reaction  with  organic  per- 
oxides,  134 

unsaturated,  reaction  with  oxygen,  54 

unsaturated,  separation  from  saturated, 

109 

Hydrogen,    selective    combustion    in    pres- 
ence of  methane,  77 

Hydrogenation  of  benzenoid  hydrocarbons, 
281 

by  Ipatiev's  method,  283,  284 

by   Skita's  method,   285 

without  a  catalyst,  49 
Hydrotropilidene,  511,  512 
Hypochlorous  acid,  reaction  with  defines, 

124 
Humulene,  412 

Ichthyol,   28,   33 

Ingold,  theory  of  valence  of  cyclic  hydro- 
carbons, 117,  118 
Inosite,   294 

Iodine  numbers  of  unsaturated  hydrocar- 
bons, 123 
lonone,  ketones  related  to,  203 

preparation,  200,  201 
Irone,   202 
Isoallofenchene,  448 
Iso-amyl-a-dehydrophellandrene,   313 
Isoborneol,  460 

from  camphene,  500,  510 
Isobornyl  acetate  from  camphene,  462 
Isobornyl  chloride,  444 

reaction  with  alkalies,  461,  462 
Isobutane,  48,  87 
Isobutene,  87 

oxide,    342 

polymerization,    210 

Isobutyl  alcohol,  decomposition  by  heat,  70 
Isocamphane,  444,  464,  489 
Isocampholytic  acid,  475,  476,  483 
Isocamphorene,   195 
Isocamphoric  acid,  472 
Iso-ethionic  acid,  143 
Isofenchene,  448,  507 
Isogeraniol,   194 

Isoheptene(l),   preparation,  152 
Isohexane,  pyrolysis,  36 
Isolaurolene,  483 
Isolauronolic  acid,  475 


SUBJECT  INDEX 


607 


Isomenthol,  360 
Isonitrosocamphor,  484 
iso-octene(l),  preparation,  152 
Isoparaffines,  22,  23 
Isopentane,  critical  constants,  548 

from  trimethylethylene,   48 
Isopentene,  from  n.pentane,  217 
Isopinene,  441,  448 
Isoprene,  chemical  properties,  177 

condensation  with  limonene,  43 

conversion  to  dipentene,  216 

dimerides  of,  227,  228 

physical  properties,  231 

polymerization,  215 

preparation,  216,  219,  221,  224 

preparation  from  petroleum,  216 

reaction  with  sulfur,   144 

separation  from  hydrocarbon   mixtures, 

Isopropyl  alcohol  from  propylene,  167,  169 

Isopulegol,  130,  192,  356 

Isopulegone,    rearrangement    to    pulegone, 

130 

Isothujone,  400,  401 
Isozingiberene,  313 

Jellies,  of  mineral  oils,  587 

Ketene,  125 

Ketones,  bromination  of  cyclic,   365 

nitration  of,  62 

physiological  action  of  certain,  597 
Kerogen,  23,  96 
Kerosene,  emulsion  of,   588 

halogen  derivatives,  69 

refining  of,   102,   131,   132 
Kishner's    reaction,    366,    372,    409,    452, 

463,  464 

Krafft's   synthesis   of   unsaturated    hydro- 
carbons, 154 

Langmuir,  theory  of  atomic  structure  and 

the  ethylene  bond,  111,  112,  113 
Latent  heat  of  vaporization   of  hydrocar- 
bons, 567 

Laurenone,  481,  482 
Laurolanic  acid,  477 
Laurolecue,  synthesis  of,  483 

series,   nomenclature  of,   475,  476 
Laurolenic  acid,  475,  476,  481 
Laurololactone,  477 
Laurololic  acid,  477 
Lauronolic  acid,  475,  476,  481 
Lewis,  theory  of  the  ethylene  bond,  111, 

112 
Light,    absorption    of,    by    hydrocarbons, 

548,  549 

Lignite  tar  oils,  action  of  ozone  on,  143 
Limonene,  condensation  with  isoprene,  43 

constitution,  319  et  seq, 

conversion  to  isoprene,  216 

dihydrochloride,  319 

hydrogenation,  48,  318,  319 

nitrolanilides  316 

nitroso-azide,    318 

nitrosochloride,  317 

occurrence,   315,  422 

oxidation  of,  318 

ozouide,   142 

physical   properties,   316,   317 

reaction  with  formaldehyde,  318 

rearrangements  through  addition  of  wa- 
ter, 130 

relations   to   a-terpineol   and    1.8-terpin, 

328 
Linalool,  chemical  properties,  195 

constitution  of,  188,  189 

conversion   to  terpinene  and  dipentene, 
195 


Linalool,  occurrence  and  identification    195 

oxidation   of,   189 

preparation  from  geraniol,  188 

reaction   with   bisulfite,   196 

synthesis  of,  189 

Linalyl  acetate,  reaction  with  sulfur,  196 
Liquid  petrolatum,  593 
Lubrication,  by  oil  films,  579 

relation  to  viscosity,  577 
Lubricating    oils,    chemical    character    of 
522,  523 

from  coal,  284 

from  tetrahydronaphthalene,  522 

formation  by  polymerization,  522 

oxidation  of,  52,  53 

refining  of,  102,  108 

resinification,   53 

viscosity  of,  578,  579 

Magnetic  rotation,  562 
Marsh  gas,  see  Methane 
Melting  points,  543 

effect  of  structural  differences,  545,  546 

effect  of  unsaturation  on,  545 

of  n.parafflnes,  544 
o.Menthadiene  AJ-8(»),  330 
m.Menthadienes,  possible.  388 

A2-«(9),  330 

*»••(•),  330,  391 
p.Menthadiene  A1  •*  (a-terpinene)    339 

A»-«(»)    synthesis,  329,  330,  331 

A»-«  d  and  I,  564 
Menthaue  carboxylic  acid,  361 

2.8-dihydroxy-2-methyl,  376 

meta  derivatives,  384 

ortho  derivatives,   392 

para,  preparation  and  properties,  319 

para,  from  cymene,  243,  282 
Menthanol(3),  para,  see  Menthol 
Menthatriene  A2-»-8(»)-2-methyl    376 

A2.e.8(9)_2-propyl,   292,   293     ' 
Menthene,  para,  As,  364 

para,  A«(8),  364 
Menthenols,  hydration  of,  129 

meta,  390 

ortho,  392 
Menthenol(S),  meta  A»,  387 

meta,  A',  391 

meta,  A«,  387 

para,  A2,  353 

para,  A«(»),  355 

para,  A«(»),  356 

para,  A»,  331,  353 
Menthanone(5),   ortho,  395 
Menthenone,  A»,  355,  367 

(2),  A«,   375 
Menthocitronellol,  363 
Menthol,  alkyl  derivatives,  360 

catalytic  dehydrogenation,   360 

crystalline  forms  of,   357 

esters  of,  362 

occurrence,  357 

oxidation,  365 

preparation    from    thymol,    358 

preparation  from  pulegone,  359,  360 

stereochemistry  of,   360 
Menthone,   alkylation  of,   360,   366 

bromination,    365 

chemical   reactions  of,    360 

CJ«  and   (ran*  forms,    358 

conversion    to    l-methyl-3-isopropyl    cy- 
clopentanone(2),  371 

conversion  to  p-mentnane,  366 

conversion  to  buchu  camphor,  371,  372 

derivatives,  characteristic,  363 

electrolytic  reduction  of,  360 

isoxime,   363 

nitration  of,  62 

normal,  367 


608 


SUBJECT  INDEX 


Merrthone,  optical  inversion  of  lavo.,  366 
rearrangement   to  cyclo-pentane  deriva- 
tives, 527,  528 
stereochemistry  of,   361 
synthesis,   364 
Menthonylamine,  363 
Menthyl  chloride,  361 
Menthyl  hydrogen  phthalate,  resolution  of, 

359 

Menthyl  phenyl  ether,  361,  362 
Menthylamine,   364 
Menthylidene  hydrazrine,  366 
Mesityl  oxide,  ozonide  of,  138 
Methane,  carbon  black  from,  78 
chlorination  of,  79 
combustion,  mechanism  of,  78 
compressibility  of,  15 
conversion  to  hydrocyanic  acid,  81 
conversion  to  formaldehyde,  78 
liquefaction  of,  76 
luminosity  of  flame,  76 
occurrence,  13,  14,  33 
oxidation  by  permanganate,  57 
physical  properties,  76,  98 
physiological  effect,  77 
preparation    from    carbon    monoxide   or 

water  gas,  81,  82 

preparation  from  cellulose,  18,  19,  31 
preparation  from  ethylene,  33,  35 
preparation   from  hexane,   35 
pyrolysis  of,   35,  78 
solubility  in  oils,  583 
solvent  power  of  compressed,  583 
warning  for  — ,  in  mine  gases,  77 
Methyl  borneol,   462,   463 
caniphene,  462 
camphenilol,   460 
camphor,  488 
carveol,   376 

chloride,  from  methane,  79,  80 
chloride,  physical  properties,  80,  81 
chloroform,    597 
cyclohexane  methyl  ketone,  237 
cyclohexeues,   276 
cyclopentane,  isolation  of,  18 
cyclopentene  methyl  ketone,  237 
(2)-dihydrocarveol,  376 
-a-fenchene,  462 
fenchyl  alcohol,  462,  463 
Methyl  group,  nitration  of,  62 
Methyl  heptenone,  condensation  of,  238 

2-methyl  heptene(2)-one(/6),  184 
2-Methyl  homolimonene,  376 
Methyl  nopinol,  438  / 

norcamphor,  450  I 

pyrollidine,  224  / 

Mexican  petroleum,  sulfur  in,  28 
Molecular  dispersion,  562 

dispersion,   effect   of   ring  closing   on — , 

554 

refraction,  550 
refraction,   effect   of   ring   closing  on — , 

553,  554,  555 

volume  and  density,  538.  539,  540 
volume,  effect  of  ring  closing  on — ,  541, 

542 

volume  of  isomeric  hydrocarbons,  539 
Montan  wax,  23 
Myrcene,  182 
Myrtenol,  437 

Mustard  gas,  physiological  action,  597 
see  also  0j8-Dichloro-ethyl  sulfide 

Naphthalene,   hydrogenation  of,  242,  283, 

404 

in  petroleum,  20,  24,  26 
Naphthanols,   preparation  and  properties, 

405 


Naphthanone  405 
Naphthenes,   280 

in  Borneo  petroleum,  38 

sulfonation  of,  63 
Naphthenic  acid,  56,  273 

optically   active,    566 

removal  from  petroleum  distillates,  104 

synthesis  of,  275,  276 
Naphthols,  hydrogenation  of,  283 
Natural  gas,  composition,  13,  14 
Neomenthol,  359 
Nerol,  186,  187 
Nickel,  effect  on  pyrolysis  of  hydrocarbons, 

Nitration,  of  non-benzenoid  hydrocarbons, 

60 

to  detect  benzenoid  hydrocarbons,  26 
Nitro  group,  effect  on  melting  point,   546 
Nitrocamphene,   465 
Nitrocyclohexane,   289 
Nitrogen   bases,   in   petroleum,  29,  103 
Nitroparaffines,  solubility  in  alkali,  61 
Nitrosochlorides,  145 

conversion  to  oximes,  147 
method  of  preparation,  146 
Nitrosolimonene,   see  carvoxime 
Nitrosopinene,   431 

Nomenclature  of  camphoric  acids,  477 
of  spiro  compounds  and   bridged  rings, 

405,   406,  407 
n.Nonacosane,  101 
n.Nonadecane,  100 
Nonadienes,  180 
Nonanes,  94,  99 
Nonene(2),  207 
Nonene(4)-4.8-dimethyl,  208 

-2.5.8-trimethyl,  208 
Nopinic  acid,  426,  445 
Nopinolacetic  acid,  445 
Nopinone,  444,  445 

conversion  to  pinene-hydrochloride,  438, 

498 

Norcamphane,  396 
Norcaradienecarboxylic  acid,  514 
Norcarane,  396 
Norpinane,  396 
Norpinic  acid,  425 

Ocimene,  182 

Ocimenol,  183 

n.Octacosane.  101 

Octadiene,  1.6^dimethyl  cyclo,  142 

A2-*-3.7-dimethyl,  232 

A2-«-3.7-dimethyl,  232 

A2-8-2.6-dimethyl,   232 

A^-2.7-dimethyl,   232 

A»-5-4-methyl,  232 

As-B-7-methyl,  232 
Octahydrindene,  243 
Octahydro-anthracene,   284 
Octane,    2.6-dimethyl,   derivatives   of,   183 

2.6-dimethyl,  oxidation,  57 

2.7-dimethyl,   nitration   of,   61 
n. Octane,  critical  constants,  548 

physical  properties,  99,  538,  548 

sulfonation,   63 

vapor  pressure,  17 

Octanes,  heats  of  combustion  of  isomeric, 
571,  572 

synthesis  of,   91,  92 

molecular  volumes  of,  539 

melting  points  and  constitution,  545 

physical  properties,  93,  99 

pyrolysis  of,  36 
Octene(l),  hydrogenation  of,  48 

physical  properties,  206 

-2-methyl,  207 
Octene(2),  hydrogenation,   48 


SUBJECT  INDEX 


609 


Octene(2),  physical  properties,  207 
2.6-dimethyl,  207 
2.7-dimethyl,  207 
3.7-dimethyl,  207 
Octene(4)-4  methyl,  207 

4.7-dimethyl,  208 
Octenes,  from  nonylenic  acid,  151 
reaction  with  sulfuric  acid,  127 
Odor,    of    unrefined    petroleum   distillates. 

102,  103,  591 

relation  of — ,  to  constitution,  203 
Oenanthol,  90 
Oil  gas,  composition,  40 
butadiene  from,  216 
chlorination,  165 
Dayton  process,  40 
effect   of   temperature   and   pressure  on 

composition,  40,  41 
experimental  production,  36 
isopropyl  alcohol  from,  167,   169 
liquid   condensate  from,   37 
time  factor  in  producing,  36 
yields  at  different  temperatures,  38,  39 
yields  in  Hall  apparatus,  40 
Oiliness.  579 
Oklahoma  petroleum,  benzene,  homologues 

in,  38 
Okonite,  96 

defines,  formation  from  alkyl  halides,  73 
in    petroleum    oils,    reaction    with    sul- 
furic acid,  106,  107 
See  also  Hydrocarbons,  unsaturated 
Optically  active  hydrocarbons,   564 
Optical  activity,  563 
Oxidation,  of  saturated  hydrocarbons,  52, 

54 

Oxides,  alkylene,  341,  342,  343 
alkylene,  formation  of,  135 
of  the  terpene  series,  341 
1.4-Oxidopentane    (tetramethylene    oxide), 

343 
1.5-Oxidopentane    (pentamethylene  oxide), 

344 

Oxycamphenilanic  acid,   465 
Oxyfenchenic  acid,   447 
Oxymethylene  camphor,  488 
Oxymethylenementhone,    366 
Ozokerite,  95,  96 
Ozone,  reaction  with  pinene,  502 
Ozonides,    decomposition    of,    137,    138 

Paraffine     hydrocarbons,     occurrence,     13, 
16,  19 

table  of  melting  and  boiling  points,  21 
Paraffine  oil,  104,  105,  593 
Paraffine,  pyrolysis  of,  39 
Paraffine  wax,  16,  18,  95 

chemical  properties,  23,  63,  102 

composition,    21,    22 

crystallization  of,  96 

dielectric  constant,  97 

effect  of  —  on   viscosity  of  lubricating 
oils,  578 

oxidation,    53,    55,   57 

physical  properties,  97 

reaction  with  sulfur,  97 

solubility  in  compressed  methane,  583 

solubility  in  various  solvents,  97,  581 
Parafflnes,  Ci0H22  to  CaoH^,  tables,  94-97 

conversion    to    benzenoid    hydrocarbons, 
26 

formation,  methods  of,  33 

formation  by  biological  processes,  18 

formation,  by  decomposition  of  other  hy- 
drocarbons, 42 

halogenation,   63,  64 

molecular  volumes,  539 

occurrence  in  essential  oils,  95,  96 


Paraffines,  physical  properties,  98,  99 

reaction  with  sulfur,  58,  59,  97 

solubility  in  liquid  SOa,  586 

syntheses,  45,  94 

viscosity,  577,  578 
Paraffinum  liquidum,  593 
Pennsylvania    petroleum    distillates     spe- 
cific heats  of,  567 
Pentacontane,  from  coal,  19 
n.Pentacosane,  101 
n.Pentadecane,   100 
Pentadiene,  A1-*,  177 

A'-'-S-methyl,  232 
Pentamethylene  oxide,  344 
Pentane,  brominatiou,  64 

chlorination,  63,  89 

from  petroleum,  20 

phvFical  properties,   98 

pyrwysis  of,   36 

separation  from  isopentane,  18,  87 

vapor   pressures,   17,   88 
Pentane,      1.4-dibromo — ,      conversion      to 
methyl  cyclobutane,  234 

1.5-dibromo,   234 

1.5  dicarhoxylic  acid,  280 

2.2-dimethyl,  nitration  of,  61 

2-methyl-3-ethyl,   93 
Pentane,  iso,  from  petroleum,  20 

1*0,  physical  properties,  98 
n.Pentane,    conversion    to    isopentane,    67, 

conversion  to  isoprene,  217 

critical  constants,  548 
Pentanes,    chloro,   conversion   to  acetates, 
74 

chloro,  decomposition,  153 

conversion  to  rubber,  217,  218 

dichioro,  219 

dichloro,  preparation.  88 
Peutatriacontane,  19,  101 
Pentene(2),  -2.3-dimethyl,  206 

-2.4-dimethyl,   206 

-3-ethyl,  127,  152,  206 

-2-methyl,  206 

2-methyl-3-ethyl,  207 

3-methyl,  206 
Pentene(S),   2-methyl,   206 
Pentene(2)-ol  (4),  223 
Perhydro-anthracene,  284 
Perillic  acid,  379 

alcohol,   379 

aldehyde,  379 

Peroxides,  organic,  formation  of,  183 
Petroleum,      filtration      through      fullers* 
earth,  30,  589,  590 

fluorescence  of,  550 

optical  activity  of,  31,  565,  566 

origin,  19,  20,  29,  30 

pyrolysis  of,  34  et  seq. 

distillates,  action  of  ozone,  142 

distillates,  decolorizing,  105 

distillates,  hydrogenation,  49 

distillates,  latent  heat  of  vaporization, 
567 

distillates,    refining   of,    102,    103,    107, 

108,  126,  131,  586 
distillates,  refractive  indices,   562 
distillates,  specific  heats,  567 
distillates,  treatment  with  sulfur  diox- 
ide, 586 

distillates,  solubility  in  various  solvents, 

580,  582 

Petroleum  jellies,  587 
Petroleums,  gases  dissolved  in,  583 
Pharmaceutical    paraffine    oil,    104,    105, 

109,  593 

Phenanthrene,  hydrogenation  of,  284 
Phellandrenes,   380  et  Beq. 


610 


SUBJECT  INDEX 


a-Phellandrene,  conversion  to  carvotanace- 
tone,  380 

molecular  refraction,   559 

nitrosite,  381 

synthesis  of,  381 
iS-Phellandrene,  381 
Phenols,  reduction  of,  281 
Phenyl  ether,  hydrogenation  of,  284 
Phthalic  acid,   hydrogenation  of,  282 
Pinacoline  alcohol,  460 
Pinacoline  rearrangement,  528-531 
Pinacone,   for   rubber   synthesis,   223,   226 
Pinacones,  cyclic,  528,  529 

intramolecular  condensation,  239 
Pinane,  429 
Pine  oil,  421 
a-Pinene,  constitution,  424  et  seq. 

conversion  to  carvone,  431,  432     „ 

dehydrogenation,   430 

dichlorohydrine,  124,  428 

hydrochloride,  438,  439,  497,  498 

hydrogenation,   429 

identification,  424 

nitrosoazide,  433 

nitrosochloride,  430,  431 

occurrence,  423 

ozonide,  427,  502 

reaction  with  acetic  acid,  501 

reaction  with  benzoyl  peroxide,  429 

reaction  with  diazoacetic  ester,  434 

reaction  with  hydrogen  chloride,  438 

reaction  with  hydrogen  peroxide,  429 

reaction  with  hypochlorous  acid,  124 

reaction  with  mercuric  acetate,  429 

reaction  with  organic  acids,  501 

reaction  with  oxalic  acid,  126,  439,  501 

reaction   with  ozone,   427,   502 
0-Pinene,  444,  445 

nitroso — ,  446 

oxidation,  426 

synthesis,  154 
Pinic  acid,  425 
Finite,  295 
Pinocamphone,  432 
Pinocamphylamine,    433 
Pinol,   348  et  seq. 

hydrate,  349,  351,  427,  428 

oxide,  427,  428 

tribromide,   conversion  to  pinolone,  350 
0-Pinolene,  439,  441,  442 

relation    to   fenchyl   and   isofenchyl   al- 
cohols,  509 
Pinolone,    350 

a-Pinonic  acid,  425,  426,  427 
Pinononic  acid,  435 
Pinoyl   formic  acid,   425 
Pintsch  gas,  37,  40 
Pinylamine,   432,   433 
Piperitone,  367,  368 
Piperylene,  177,  223,  231 

dimeride  of,   228 
Polymerization,  different  types  of,  229 

by  surfuric  acid,  127 

in  refining  petroleum  oils,  106,  137 

influence  of  oxygen,  226 

of  olefines  by  aluminum  chloride,  45 

of  olefines  by  heat  and  pressure,  42 
Polymers,  source  of,  in  refined  oils,  131 
Polynaphthenes,  522 
Producer  gas,  composition  of,  40 
Propane,  85 

in  natural  gas,  14 

physical  properties,  85,  98,  540,  548 

pyrolysis,  41 

synthesis,  48 

l-bromo-2.2-dimethyl,  72 

2.2-dimethyl,  98 

1.2-diphenyl,  62 


Propane,  1.2.3-trichloro,  86 
Propanol(l)-sulfonic  acid (2),   143 
Propyl  bromides,  decomposition,  69 
Propylene,  1  and  2  chloro,  86 

chemical  properties,  169,  170 

chlorohydrines,   124,  170 

conversion  to  isopropyl  alcohol,  167,  169 

hydrogenation,   48 

in  oil  gas,  37,  40 

liquid,  vapor  pressures,  85 

physical  properties,  540,  548 

preparation,   169 

reaction  with  HBr.,  68 

reaction  with  hydriodic  acid,  66 

reaction  with  nitrosyl  chloride,  146 
Protoparaffine,  22,  96 
Pseudo-ionone,   201 
Pseudo-pelletierine,  519 
Pulegene,   369,   370 
Pulegenone,  370,   372 
Pulegoue,  conversion  to  carane,  372 

conversion    by    hydrogenation    to    men- 
thols,  359 

conversion  to  A3-p.-menthenol(3),  332 

conversion  to  pulenone,  368 

ozonide,  138 

physical   properties,   368 

sulfonic  acid  derivative,  144 
Pulenone,  368,  369 
Pyrolysis,  effect  of  pressure,  42 

effect  of  metals,   43,  44 

in  presence  of  steam,  44,  45 

of  petroleum  oils,  34,  42,  44 

Racemization,   of  hydrocarbons,   564 
Rearrangements,  by  addition  of  water,  130 

borneol  to  camphene,  532 

of    carbocyclic    structures,    theories    of, 

526,  528,  529 
chloroketones,  527 
cyclobutylamine   to   cyclopropylcarbinol, 

525 
cyclobutyl-methyl   amine   to   cyclopenta- 

nol,  525 
cyclobutyl-diethyl  carbinol  to  1.1-diethyl- 

A2-cyclopentene,   524 
cyclobutyl-dimethyl    carbinol    to    1.2-di- 

methyl-Ai-cyclopentene,    524 
cyclobutyl    carbinol    to    bromocyclopen- 

tene,  524 
cycloheptyl   iodide   to   methyl   cyclohex- 

ane,   524 

cyclohexane  to  methyl  cyclopentane,  524 
cyclohexanes  to  cycloheptanes,  530 
cyclohexanones  to  cyclopentanones,   536 
2.2-dimethyl  cyclohexanol(l)    to  isopro- 

pyl-Ai-cyclopentene,   534 
2-chlorocyclohexanone    to    cyclopentane- 

carboxylic  acid,   527 
cyclohexylmethyl     amine     to     cyclohep- 

tanol,  525 
cyclopentanes  to  cyclohexanes,  433,  529, 

535 

cyclopentyl  carbinol  to  cyclohexene,  526 
cyclopentylmethylamine  to  cyclohexanol, 

525 
cyclopentyl    nitrite    to    nitromethyl    cy- 

clobutane,    525 
dibromo  cyclic  ketones,   527 
2.2-dimethyl-l-chloropropane    *to    2-me*- 

thyl-2-chlorobutane,   463 
2-iodocyclohexanol  to  cyclo-pentyl  alde- 
hyde, 526 

ethylene  oxide  derivatives,  531 
isoborneol  to   camphene,   463 
menthone  to  cyclopentanone  derivative, 

527,  528,  537 
pinacoline,   528 


SUBJECT  INDEX 


611 


Rearrangements,  .  pinacoline     alcohol      to 
tetra-methyl  ethylene,  532,  534,  535 

retropinacoline,    463 

the  Wagner,  528  et  seq. 
Refining  of  petroleum  distillates,  102,  126, 
131 

effect  on  specific  gravity,  107 

by  sulfur  dioxide,  586 

effect  of  nitric  acid,  108 

effect  of  temperature.  108 
Reformatsky's   reaction,   154,   366 
Refractivity,    Eisenlohr's    revised    values, 

551 

Refractive    indices    of    conjugated    dienes, 
292 

effect  of  ethylene  bond,  551,  552 

effect  of  ring  closing,  553-557 

exaltation  caused  by  conjugation  of  CO 
and  ethylene  bond,  559 

of  petroleum  distillates,  562 

of  semi-cyclic  double  bonds,  560,  561 
Retene,  418 

Retropinacoline  rearrangements,  463 
Rhodinol,   190,   191 

Ring   formation,    effect    on    boiling   point, 
547 

effect  on  melting  point,  545 

effect  on  molecular  refraction,  553-557 

effect  on  molecular  volume,  541-542 

effect  on  viscosity,  578 

methods  of,  233  et  seq. 

by   polymerization,    212 
Rosin   oil,   303,   418,  419 
Rosin  spirit,  419,  421 
Rubber,  behavior  in  various  solvents,  584 

chlorinated,    123 

destructive  distillation,  216 

ozonides,  142.  214 

plantation,  214 

reaction  with  sulfur  chloride,  136 

solutions,  viscosity  of,  584 

synthetic,  214  et  seq.,  225 
Rubbers,  synthetic,  classification,  215 

synthetic,  from  petroleum,  216 

synthetic,  vulcanization  by  sulfur.  136 

synthetic,  vulcanized,  sulfur  in,  ob4 

Sabina  ketone,   399 

Sabinane,  553 

Sabinene,  oxidation  products,  399 

physical  properties.  553 

sulfonic  acid  derivative,  144 
Santalene,  o  and  /3,  415 

0  from  a-phellandrene  and  isoprene,  416 
Santalols,  a  and  j3,  416 
Santene,   397 
Selinene,  413,  414 
Sesquicitronellene,  204 
Sesquiterpenes,  310  et  seq. 

Sludge,  from  petroleum  refining,  103 
Sobrerol.  see  Pinol  hydrate 

in  suKur  dioxide, 


petroleum  fractions  in  ethyl  alcohol  and 

acetic  anhydride,  580,  581 
solids  in  compressed  gases,  583 
Specific  heat,   566,  567 
Specific  viscosity   of  hydrocarbons,   577 
Spectra    absorption,  of  hydrocarbons,  548, 

549 

Spinacene.  204 
Spiro  and  cyclopropane  derivatives,  rela- 

tive stability,  116,  117 
Spirocyclene,  252 
Squalene,  see  Spinacene 
Stearoptene,  19 


Styrene,  oxidation  and  polymerization,  134 

Suberone,  see  Cycloheptanone 

Suberyl  alcohol.  511 

Sulfonation  of  hydrocarbons,  63 

Sulfonic  acids,  144 

Sulfur,  colloidal,  in  oils,  105 
colloidal,  in  rubber,   137,  584 
in    petroleum   distillates.    27,    103,    106, 

107 

derivatives,    effect    of    aluminum    chlor- 
ide on.  45 

Sulfur    dioxide,    liquid,    for    refining    oils, 

109,  586 

reaction  with  ethylene  bond,  59 
reaction  with  paraffines,  58.  59 
solubility  in  hexane,  583 
state  of,  in  vulcanized  rubber,  584 

Sulfuryl    chloride,    as    a    chlorinating    re- 
agent, 165 
catalysts  for  preparation,  366 

Sylvestrene.  384  et  seq. 
synthesis,  386,  389,  390 

Sylveterpin,  389.  390 

Sylveterpineols,  390 

Terpenes,  absorption  spectra  of,  549 

autoxidation,  134 

comparison    with   aliphatic   unsaturated 
hydrocarbons,  174  et  seq. 

general  reactions  of,  174  et  seq. 

rearrangements  by  hydration,  130 
Terpenylic  acid,  325,  326 
Terpin,  1.4,  336,  337 

1.8,   319 

synthesis,  320,  323 
Terpinene,  from  linalool,  195 
o-Terpinene,  from  thymohydroquinone,  340 

molecular  refraction,  559 

oxidation,   338 

transformation  to  carvenone,  339 
7-Terpinene,  339,  340 
Terpinenes,  333,  335-337 
Terpinenol(l),  355 
Terpinenol(4),  338,  354,  355 
Terpineols,  para,  351 
o-Terpineol,  chlorohydrinc  of,  351 

conversion  to  carvone,  329 

conversion  to  terpin  hydrate,  323 

constitution,   320,   321 

dibromide,   349 

identification,  322 

occurrence  and  properties,  321,  322 

occurrence  in  pine  oil,  421 

preparation,  424 

nitrosochloride.  329 

oxidation,  324 

synthesis,  320  et  »eq. 

fl-Terpineol    properties  and  synthesis,  352 
•y-Terpineol,  334,  335,  353 
Terpin  hydrate,  323,  324 
Terpinolene,  333-335 
n.Tetracosane,  100 
n.Tetradecane,  100 
Tetradecene(l),  208 
Tetrahydro-anthracene,    284 
Tetrahydrobenzene,  see  Cyclohexene 
Tetrahydrocarvone,  356 
Tetrahydrocitral,  200 
Tetrahydro-eucarvone,  374,  517,  519 

conversion    to    dimethyl   cyclohexanone, 

374 

Tetrahydrogeraniol,  200 
Tetrahydronaphthalene,  242,  404 

reaction  with  formaldehyde,  522 
Tetrahydrosantalene,  416 
Tetrahydroterephthalic  acids,  278 
Tetrahydro-xylene,  meta,  308 
Tetramethyl  allene,  212 


612 


SUBJECT  INDEX 


Tetramethylene  oxide,   343 
Tetramethyl  ethylene,  72,  532 

physical  properties,  206 

preparation,  460 

reaction   with  n.  bromo  acetamide,   123 

reaction  with  sulfuric  acid,  126 
Tetramethyl   methane,   46 
Tetratriacontane,   101 

Thermochemistry  of  non-benzenoid  hydro- 
carbons, 117,  568 
Thiophanes,  28 
Thiozonides,   135 
Thujamenthols,  401 
Thujane,  402 
Thujene,  400,  402 
Thujone,   400,   401 

physiological  action,  594 
Thurlow   process,   for  synthetic   camphor, 

501,  505 

Thymol,  hydrogenation,  358 
Toluene,    conversion    to    methyl-cyclohep- 
tatriene,  514 

from  methyl  cyclohexane,  43 

from  petroleum,  37 

hydrogenation  of,  282 
Transformer  oils,  oxidation  of,  52,  53 

water  in,   53,  54 
n.Triacontane,  101 
Triazo-ethylene,  163 
Trichloro-ethylene,   122 
n.Tricosane,  100 
Tricyclal,  443 
Tricyclene,  439,  443,  444,  460,  461 

from  fenchyl  alcohol,  508 
Tricyclenic  acid,  443 
Tricyclol,  443 
n.Tridecene,  99 

Trienes,  molecular  refraction,  557,  558 
2.6.6-Trimethyl-0.1.3-dicyclohexane,    409 
Trimethylene  oxide,  343 
Trimethylethylene,  217 

hydration  of,  125,  131 

hydrogenation,  48 

oxidation,  135 

preparation,  72,  131 

reaction  with  HC1,  67 
n.Tritriacontane,  101 
Tropidene,  exhaustive  methylatlon,  512 
Tropilidene,  512 
Tropine  bases,  512 
Trouton's  rule,   542,  543 
Tschugaeff's  synthesis  of  un saturated  hy- 
drocarbons, 154,  455 
Tung  oil,  polymerization,   213 
Turpentine,  American,  421 

autoxidation,   133,   428,   429 

conversion  to  camphor,  495 

French,  422 

from  copals,  422 

Greek,  423 

optical  activity  of,  563 

physical  properties,  422 

production,  420 

purification,  497 


Turpentine,  pyrolysis.  216,  430 

reaction    with    hydrogen    chloride,    497, 

reaction  with  oxalic  acid,  501 

reaction  with  sulfur,  135 

"recovered,"   421 

Russian,  422 

solubility  in  alcohol,  582 

substitute,  94 

Swedish,  387,  422 

tests  for  purity  of,  495 

wood,   421 

n.Undecane,  99 
Undecene(l),  208 
Undecene(2),    208 

-2-methyl,  127 

Unsaturation,  effect  on  physical  constants, 
545,   548 

Vanillin,  synthesis  by  ozone,  142 

Vaporization,  latent  heat  of,  567 

Vaseline,  composition,  17 

Verbenene,  435,  436 

Verbenol,  429 

Verbenone,    429  435 

Vestrylamine,  385 

Vinyl  acrylic  acid,   polymerization,   236 

Vinyl  bromide,  polymerization,  211 

reaction  with  HBr,  69 
Vinyl    chloride,    reaction    with    ammonia, 

Vinyl  halides,   polymerization,   122 
Viscosity,  576 

effect  of  pressure  on,  580 

effect  of  ring  closing  on,   578 

relation    to    lubrication,    577 

rubber  solutions,  584 
Vulcanization  of  rubber,  136,  584 

Wagner  rearrangement,  528,  532-534 
Walden  inversion  in  case  of  bornylene,  504 

carvoxime,   375 
Water  gas,  composition,  40 

conversion  to  methane,  81,  82 
Wax,  amorphous,  18,  22,  96 

bee's,  19 

candelilla,   19 

ceresine,  22 

montan,    23 

paraffine,  21,  22,  23,  34,  95 
Wood  turpentine,  421 
Wurtz,   synthesis  of  hydrocarbons,   50 

Xylene,  para,  conversion  to  dimethyl-cyclo- 

heptatriene,    514 

para,    reaction    with    diazoacetic    ester, 
514 

Zinc  alkyls,  46 

Zinc  chloride,  effect  on  pyrolysis,  45 

Zingiberene,  311,  312 

Zingiberol,  311,  312 


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